Chemistry Homework Help


Questions

# Description Question
16965

Calculate the pH after 0.017 mole of HCl is added to 1.00 L of each of the four solutions. (Assume that all solutions are at 25°C.)

(a)    0.133 M acetic acid (HC2H3O2Ka = 1.810−5)
 

(b)    
0.133 M sodium acetate (NaC2H3O2)
 

(c)    pure H
2O
 

(d)    
0.133 M HC2H3O2 and 0.133 M NaC2H3O2

 

Consider a solution that contains both C6H5NH2 and C6H5NH3+. Calculate the ratio [C6H5NH2]/[C6H5NH3+] if the solution has the following pH values. (Assume that the solution is at 25°C.)

(a)    pH = 5.16
 

(b)    pH = 
5.53
 

(c)    pH = 
4.74
 

(d)    pH = 
4.93

 

Consider the titration of 41.5 mL of 0.198 M HCl with 0.124 M NaOH. Calculate the pH of the resulting solution after the following volumes of NaOH have been added. (Assume that all solutions are at 25°C.)

(a)    0.0 mL
 

(b)    10.0 mL
 

(c)    40.0 mL
 

(d)    80.0 mL
 

(e)    100.0 mL

Consider the titration of 100.0 mL of 0.240 M benzoic acid (Ka = 6.410−5) with 0.120 M KOH. Calculate the pH of the resulting solution after each of the following volumes of KOH has been added. (Assume that all solutions are at 25°C.)

(a)    0.0 mL
 
(b)    50.0 mL
 

(c)    100.0 mL
 

(d)    150.0 mL
 

(e)    200.0 mL
 

(f)    250.0 mL

 

Calculate the pH at the halfway point and at the equivalence point for each of the following titrations. (Assume that the temperature is 25°C.)

(a)    101.1 mL of 0.17 M HF (Ka7.210−4) titrated with 0.17 M KOH

halfway point    

 

equivalence point    

 


(b)    
100.7 mL of 0.15 M C2H5NH2 (Kb = 5.610−4) titrated with 0.30 M HNO3

halfway point    

 

equivalence point    

 


(c)    
100.9 mL of 0.51 M HCl titrated with 0.26 M KOH

halfway point    

 

equivalence point    

 

 

 

 

 

 

 

 

Calculate the solubility of each of the following compounds in moles per liter. Ignore any acid-base properties.

(a)    Ca3(PO4)2Ksp = 1.310−32
 mol/L

(b)    
MgF2Ksp = 6.410−9
 mol/L

(c)    
AgBrKsp = 5.010−13
 mol/L

 

The Ksp for silver chromate (Ag2CrO4) is 9.010−12. Calculate the solubility of silver chromate in each of the following.

(a)    water
 mol/L

(b)    
0.15 M AgNO3
 mol/L

(c)    
0.34 M Na2CrO4
 mol/L

 

 

Use the following data to calculate the Ksp value for each solid.

(a) The solubility of MnCO3 is 1.110−3 g/L.
 

(b) The solubility of 
Al(OH)3 is 5.510−9 mol/L.

 

 

The concentration of Ba2+ in a solution saturated with BaF2(s) is 1.8210−2 M. Calculate Ksp for BaF2.
 

 

 

 

 

 

 

Calculate the solubility (in mol/L) of Co(OH)3 (Ksp = 310−43) in each of the following. (Assume that all solutions are at 25°C.)

(a) water (assume pH is 7.0 and constant)
  mol/L

(b) a solution buffered at pH = 
5.5
 mol/L

(c) a solution buffered at pH = 
10.9
 mol/L

 

 

 

 

 

Calculate the pH after 0.017 mole of HCl
16621

 

Individual Case Study Homework

50 pts

CHE 432 - Spring 2018

Choose one unique topic (different from your classmates) from one of the two categories below.

·        Describe a chemical-related safety or environmental hazard that is related to your design

project. Suggested content:

o        Background of the process and plant

o        Chemical involved

o        What caused the disaster?

o        What impact did the disaster had on the local population, society, environment, and chemical industry?

o        How a better design could have prevented such a catastrophe, etc.?

o        Example: If you reactor involves catalyst, you could summarize a CSB report on an incident involving reactors using solid catalysts. Alternatively, rather than a specific incident, you may elect to describe a chronic chemical issue (e.g. acid rain, lead in gasoline, etc).

·        OR Report on a current event related to chemical engineering and the social and political implications.

o        Be as non-biased as possible.

o        Support the various views on the topic with information. Discredit non-logical claims with information.

o        Example: Potential elimination of funding for the Chemical Safety Board in 2019. (A House committee funded it in July oflast year.)

If you have another topic which you think is interesting but does not meet these criteria exactly, please check with your instructor for approval.

·        Write no more than 1 page of text. Use photos, figures and diagrams as appropriate (this will increase the page count ifused).

·         Scored on:

o        How does the topic relate to your design project or your area of interest?

o        Technical description and how clearly presented.

oClear guidance on how the topic could be preventedlimproved in the future. • Upload your file to Canvas by the due date.

Individual Case Study Homework
16361

Writing Assignment

Chem111

Sp 2018

For two weeks (ten days), I want you to keep a record of your diet.  Try to track everything you eat and how much of it.  You can use choosmyplate.gov or any other app or program to assist.  The ultimate goal is to do a detailed analysis of your diet.  We would like to know, at a minimum: your total caloric intake, fat intake, carb intake, protein intake.  It would be best if we could get data on your vitamins and minerals as well.  Your recording and paper can include exercise as well but is not required.

Once you have acquired the minimum two weeks-worth of data, I would like you to analyze your diet in the following manner:

Part 1:   Report your daily averages in a chart.  Analyze your dietary trends, short-comings and indulgences.  Were you consistently healthy in your food choices? Did you get enough variety?  Did you moderate your intake?  Try to be as reflective as possible by being honest about your diet and using what we have learned in class.  Propose and actual diet to meet your goals or plans.  This should be based on your analysis and should break down the number of calories, fat, protein, carbs.  It should also address foods you need to eliminate and some that you may want to add. 

Part 2:  Suggest changes that you would or should make to your diet to live a healthier life or to meet a particular goal.  Be sure to address short- and long-term changes as well as a plan for how they should be made (e.g. should you change all of your meals at the same time and start working out or should you slowly change your lifestyle?)  I also want you to address the possible negative outcomes of your current lifestyle/diet.  Are you at increased risk of any diseases or disorders?  Discuss one of these disorders/diseases and describe the current medical practice for treating/curing the disease.  Make sure dietary changes are one of the points of discussion.

Total document length should be approximately five to seven pages. 

No particular format is required though I do want you to be consistent throughout the paper. 

You are also required to have at least two references other than the book.  One of them must come from peer-reviewed literature (a scientific journal).

The due date for the paper is the day of the final.  Papers can be submitted online.  No late submissions will be accepted.

Writing Assignment Chem111 Sp 2018
16001

Chemistry Mid-term Exam                                                                            Version 11/2016

Name:

Student number:

Directions:  It is important that you provide answers in your own words.  Please focus only on information from the text/eBook to create your own solutions.  Please do not use direct information from an outside source (especially copying and pasting from an “answer” website). Use of direct information from an outside source is against school policy.  All answers will be checked for plagiarism.  Instances of plagiarism can result in probation or possible dismissal from the school.

Please be sure to follow all guidelines (number of sentences/showing all calculations) and to provide the correct metric units of measure.  All questions are 3.33 points (.33 point for units).

 

 

1.      Experimental Design:  From the work you have done this semester, choose a topic and design an experiment you would be able to perform.  In your design (1) state your hypothesis, (2) identify your dependent and (3) independent variables, (4) your control conditions and (5) describe your experimental procedure.  You do NOT have to actually complete the experiment, just describe it with the application of the terms above.

 

 

 

2.      Perform this operation and report the answer to the correct number of significant figures:  What is the mass of a cube of aluminum that is 4.0 cm on each edge?  The density of aluminum is 2.7 g/cm3.  Show all calculations leading to an answer.

 

3.  Explain why a model of the atom is crucial to understanding chemistry and in explaining the behavior of matter.  Use 3 - 4 sentences in your explanation.

 

4.      What parts of Dalton’s atomic theory no longer agree with the current picture of the current picture of the atom? Provide an answer using at least 3 to 4 complete content related sentences in your own words.

 

5.      If an element has 12 protons and 17 neutrons, how many electrons must it have?

 

 

6.      Why are the atomic masses of elements usually decimal numbers? Provide an answer using 3 – 4 sentences in your own words.

 

 

7.      In 3 – 4 sentences and in your own words describe how Mendeleev’s periodic table differs from Moseley’s.

 

 

8.      What is the electron configuration of the element with 27 protons?

 

 

9.      How many electrons are in the highest energy orbital of the element copper?

 

 

10.  How many dots should be indicated in the electron dot structure of arsenic?

 

 

11.  Why is the first ionization energy of a nonmetal much higher than that of an alkali metal in its same period? Provide an answer using 3 – 4 sentences in your own words.

 

12.  Why do compounds with strong intermolecular attractive forces have higher boiling points than compounds with weak intermolecular attractive forces? Provide an answer using 3 – 4 sentences and in your own words.

 

 

13.  Write the formula for iron (III) sulfate.

 

 

 

14.  What is the reason the group 13 metals have a typical charge of 3+?

 

 

 

15.  Why does one mole of carbon atoms have a smaller mass than one mole of sulfur atoms?

 

16.  What is the percentage of nitrogen in N2O?  Show all calculations leading to an answer.

 

17.  How many non-bonding electrons does phosphorus have?

 

 

 

18.  Complete and balance this reaction:  sulfuric acid reacts with barium chloride

 

 

 

19.  Identify the precipitate in this reaction:  calcium nitrate reacts with sodium phosphate.

 

 

 

20.  The following is a Limiting Reactant problem:

Magnesium nitride is formed in the reaction of magnesium metal with nitrogen gas in this reaction:  3 Mg(s) + N2(g) à Mg3N2(s)

            How many grams of product are formed from 2.0 mol of N2 (g) and 8.0 mol of Mg(s)?                     Show all calculations leading to an answer.

 

21.   List 3 indicators of a chemical change.

a.     _____________________

b.     ____________________

c.     ____________________

 

 

 

22.  Check the following problem for errors. If you find an error, identify it, tell why it is an error and correct the error solving the problem correctly.  Convert 0.45 g zinc hydroxide to moles. (Hint: there are errors)

 
 

 

 

 

0.65 g ZnOH            82.41 mol        = 3.22 X 10 25 mol

                                 6.02X1023 g

 

 

23.   What is an ion?  Explain how ions form. Distinguish between a cation and an anion. Be sure to use at least 3 to 4 complete content related sentences in your explanation.

 

24.   Write the symbol for the ion formed when each element gains electrons and attains a noble-gas electron configuration.

a.       Br

b.      H

c.       Se

 

25.   Name each of the compounds.  There are ionic, covalent and acid/base compounds in the list.

a.       N2H4

b.      PI3

c.       LiOH

26.   Classify each chemical equation as a combination/synthesis , decomposition, single replacement, double replacement, or combustion.

 

a.       Pb(s) + Hg2SO4(s) à PbSO4(s) +2 Hg(l)

b.       NaCl(aq) + AgNO3(aq) à AgCl(s) + NaNO3(aq)

c.       2 H20(l)à2 H2(g) + 02(g)

            

 

 

27.   Find the molar mass of nitric acid (HNO3).

 

28.  Avogadro’s number refers to ___.

a.    the maximum number of electrons that all of an atom’s energy levels can accommodate

b.    the number of protons and neutrons that can fit in the shells of an atom’s nucleus

c.    the number of particles in one mole of a substance

d.    the number of particles in exactly 1.0 g of a substance

 

 

29.    How many moles of oxygen atoms are in 1.5 moles of CO2? (Sc2c)

a.       1 mol                     b. 1.5 mol            c. 2 mol                 d. 3 mol

 

30.   What is the mass of 0.28 mol of iron ?

Please answers these questions. No plagiarism
15744

I want to do academic paper from 15 pages about nitrogen radicals and it should not contain plagiarism and not puplished before and put the reference beside each information by use mendly program also I want to use the reference from American chemical society and royal society, and refrase all of words by your words and use chem draw to write reactions and mechanisms if you can do it tell me please

Title: Nitrogen radicals
Abstract
Introduction about general free radicals and after that write introduction about nitrogen radicals in organic chemistry
History
Methodology
Classification
Synthesis of som free radicals compounds with the reaction and mechanisms and use chem draw for structure
Many Applications of nitrogen free radicals and reactions and write structure by chem draw and explain two of them by long paragraph

Conclusion

It should use references from American chemical society and royal society or other scientific web sites science finder or direct or Willy
, and write it by your words , and write beside each information the number of reference by mendly and the link of references

I want to do academic paper from 15 pages about nitrogen radicals and it should not contain plagiarism and not puplished before and put the reference beside each information by use mendly program also I want to use the reference from American chemical society and royal society, and refrase all of words by your words and use chem draw to write reactions and mechanisms if you can do it tell me please

Title: Nitrogen radicals
Abstract
Introduction about general free radicals and after that write introduction about nitrogen radicals in organic chemistry
History
Methodology
Classification
Synthesis of som free radicals compounds with the reaction and mechanisms and use chem draw for structure
Many Applications of nitrogen free radicals and reactions and write structure by chem draw and explain two of them by long paragraph

Conclusion

It should use references from American chemical society and royal society or other scientific web sites science finder or direct or Willy
, and write it by your words , and write beside each information the number of reference by mendly and the link of references

I want to do academic paper from 15 pages
14549

 

This assignment will allow you to demonstrate the following objectives:

 

Ø  Evaluate the evolution of technologies related to solid waste management.

Ø  Describe best practices of solid waste management in an urban society.

 

Instructions:     Municipalities make every effort to best use resources and technologies in their management of non-hazardous wastes.  It can take 5 five to 10 ten years to construct and to permit a new landfill site.  It is to everyone’s advantage to use the space in a manner that the right types of waste are disposed of and that compaction levels of the waste are high. This is accomplished when easily degradable wastes are composted, when particle sizes are uniform and every opportunity is made to remove recyclable content.  The technologies in this chapter are examples of the available tools that engineers use to accomplish these objectives, and this assignment will allow you to further explore this topic.

 

Answer the questions directly on this document. When you are finished, select “Save As,” and save the document using this format: Student ID_Unit# (ex. 1234567_UnitI). Upload this document to BlackBoard as a .doc, docx, or .rtf file. The specified word count is given for each question. At a minimum, you must use your textbook as a resource for these questions. Other sources may be used as needed. All material from outside sources (including your textbook) must be cited and referenced in APA format. Please include a reference list after each question.

 

 

1)     Consider the residential waste components (1st column in Table 2-6 on page p. 53 in the textbook) and answer the following questions: (Your total response for all parts of this question should be at least 300 words.)

 

a.     What components of mixed municipal solid waste (MSW) are rejected in storage and sent via truck to the landfill?

b.    What components pass through the trommel screen? What components are screened out through the trommel screen?

c.     What components that passed through the trommel screen are captured in the magnetic separator? What components are sent to the flattener?

d.    What components are removed in the sorting step? See Figure 5-38 (on p.age 225) for additional details.

e.     What materials pass through the sorting step and go into the Hammermill shredding operation?

f.     What materials are separated in the air classifier operation?

g.    How do these processes demonstrate best practices of solid waste management?

 

 

2)     A local municipality has plans to annex a suburb community of 80,000 people. Neither the municipality nor the community has a curbside recyclinge program as they both put all of their refuse into the trash bin for collection. The municipality hand sorts the refuse and recognizes that they it will need to hire new employees and establish a budget to hand sort a larger amount of waste. Assume the following: (1) hand sorting is done 8 eight hours per day; 5 five days per week and (2) employees are paid $21/hr, and that includes allotted benefits. (For Parts A and B of this question, show all of your work.)

 

a.     How many new full-time employees will need to be hired?

b.    What additional budget should be planned to cover the cost of the new employees?

c.     What do you think would happen if these additional employees were not hired? Describe how this would affect the municipality and why it is best to hire these additional employees. (Your response for Part C of this question should be at least 100 words).

 

 

3)     Your facility has purchased an air classification system with a fan that can generate an air flow rate in the system that goes up to 15 ft/sec. Your hammermill Hammermill shredder is able to provide a wastestream containing plastic that passes a 2 cm grate. The density of the plastic is 0.955 g/cm. The facility does not have the means to conduct a drop test, but as the site consultant, they want you to make your best estimate about whether the unit will separate out the plastic from the shredded waste. Show all work before you give your estimate. (Your total response for all parts of this question should be at least 200 words.)

 

 

4)     Describe how the terms coding and switching are used in relation to MSW. Show how these terms apply to picking and hand- sorting operations, and describe best practices for each. (Your total response for all parts of this question should be at least 200 words.)

 

 

5)     a. Describe how these separation technologies have evolved over the last decade. Include the factors that are driving the development and commercialization of these operations to be used in treating municipal solid waste.

 

b. In your opinion, which of the separation technologies in use today would qualify to be classified as best in class? State your criteria for what qualifies as best in class and state your reasons for your selection. (Your total response for all parts of this question should be at least 200 words.)

Separating Plastic From

 

Shredded Waste

 

CSU Math Center | 1- 800-977-8449 x6538 |  [email protected]u Math Center Requests:  Math Center Request Form

 

 

This electronic presentation to be used with Worrell/Vesilind/Ludwig. Solid Waste Engineering: A Global Perspective, SI Edition, 3E. From Worrell/Vesilind/Ludwig. Solid Waste Engineering: A Global Perspective, SI Edition, 3E. © 2017 Cengage Learning, a part of Cengage Learning, Inc. All rights reserved. Reproduced by permission. Text/images may not be modified or reproduced in any way without prior written permission of the publisher. www.cengage.com/permissions

LINK:  http://columbiasouthern.adobeconnect.com/p84543yyqaq/

 

 

Problem: Your facility has purchased an air classification system with a fan that can generate an air flow rate in the system that goes up to 20 ft/second. Your Hammermill shredder is able to provide a waste stream containing plastic that passes a 3 cm grate, if the density of the plastic is 0.875 g/cm. The facility does not have the means to conduct a drop test, but as the site consultant, they want you to make your best estimate if the unit will separate out the plastic from the shredded waste. Show all work.

 

Solution: We will use the terminal velocity empirical equation (see pp. 203-204) Vs = 1.9 + 0.092 s + 5.8A

 

where    Vs is the terminal settling velocity of material in units of ft/sec s is the particle density in units of lb/ft3

 

A is the particle area (length x width) in units of in2

 

 

(1) Convert the plastic density from g/cm to lb/ft3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

12    .

3

 

1

 

 

 

s in lb/ft3   = 0.875

 

 

× (2.54

 

 

)

× (

 

)

×

 

 

=   .

 

 

  3

 

 

454

 

 

 

 

 

 

2

 

 

 

 

 

 

 

 

 

(2)  A in in2 = 3×

3

× (

1    .

)

 

=  .      .

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.54

 

 

 

 

 

 

 

 

 

 

                                   

 

(3)     We can now use the terminal velocity equation and plug in our calculations:

 

Vs  =

1.9

+

0.092 s  +  5.8A

=

1.9

+

(0.092 x 54.6) +  (5.8 x 1.4)

 

=  15.04 ft/sec

 

Therefore, since the Vs = 15.04 ft/sec, this is less than the 20 ft/sec airflow rate in the air classification system. This means the unit will separate the plastic from the shredded refuse.

This requires us to understand a formula. Terminal velocity empirical equation, which you can also review on pages 203-204. So, our facility has purchased an air classification system with a fan that can generate an air flow rate in the system that goes up to 20 feet per second. Your hammermill shredder is able to provide a waste stream containing plastic that passes a three centimeter grate, if the density of the plastic is 0.875 grams per centimeter. The facility does not have the means to conduct a drop test, but as the site consultant, they want you to make your best estimate if the unit will separate out the plastic from the shredded waste. So that’s why we will use the terminal velocity empirical equation.

 

And “Vs” is the velocity, the settling velocity, and it’s in feet per second units. The 1.9 is a constant as is the 0.092. The, I want to call this rho, it looks like a “P” but it’s Greek symbol rho, is the particle density in units of pounds per cubic feet. Anytime you see rho, you’re going to know that it’s talking about density. But anyway, so you’re literally going to take this constant, .092, and multiply it by whatever we figure out the particle density in units are. Then, the “A” is the particle area, usually in length times width and units of inches squared.

 

So, you will take whatever you calculate “A” to be and you multiple it by 5.8. So, you’re literally going to multiply these two values together, multiple these two values together, and then add across. Okay?

 

So the first thing we want to do is go ahead and calculate the particle density, and we have the particle density in terms of grams per centimeters and we need them in terms of pounds per feet, so that’s why we have this conversion going on here. So, we have our grams per cubic meter, and notice this, I got my cubic meter here, but notice this right here just says centimeter, but you have to cube the whole answer, so you’re literally doing 2.54 cubed, so you might want to calculate this first. And write the answer down. The same with this. This is 12 inches and we need it to be cubic feet. So, 12 inches is a foot, but we have to convert it to cube, so that’s why it’s to the third power. Now, notice that the grams go away. The inches go away. The centimeters go away, the units, and what are we left with? Pounds per feet, and it’s cubic feet because when you do this three times, it will make this a cube.

 

So, literally what you’re doing is taking .875, multiplying it by the answer to this, 2.54 cubed, and then 12 cubed. Okay, then you’re going to divide it by 454 to get 54.6 pounds per cubic feet.

 

So, that’s what our particle density is. That’s going to be multiplied to this .092. Okay? Now, let’s go ahead and calculate “A,” and “A” is going to be in units of inches squared. We started with 3 centimeter grate. So it’s three times three. Why? Because it’s length times width. So, we do 3 centimeters times 3 centimeters and then here’s our conversion, 2.54. Notice you have to do the whole thing, so it would be 1 divided by 2.54, and then square that answer. Okay? And that’s how you get that 1.4 inches squared and notice the centimeters go away. There’s 2 centimeters here; there’s 2 here. Remember, this becomes squared because of that. So you’re literally taking nine, three time three is nine, and you divide it by 2.54 squared, and you get 1.54 inches squared.

 

Now, we have the numbers needed. We have our 54.6, and we have our 1.4. And then you just plug it into the formula, so I would multiply this first, then multiply this first, add them together then add the 1.9, and you get 15.04 feet per second.

 

Now, what does it say up here? As long as it is less than this flow rate of 20 feet per second, and 15.04 is, so this means the unit will separate the plastic from the shredded refuse.

 Evaluate the evolution of technologies related to solid waste management.
14548

CHEMISTRY 145L                                                                                                            SPRING 2018

 

Lab 2B: Read the Label

 

In this experiment you will be introduced to sources of information relative to chemicals, with particular attention paid to health and safety aspects of chemical handling. You will carry out an in-depth survey of three chemicals. They are fairly common chemicals that are widely used in enormous quantities in this country in various types of manufacturing or industrial processes.

 

Choose three of the following six chemicals:

 

•

Phosphoric Acid

•

Benzene

•

Sodium Cyanide

•

Methanol

•

Sulfuric Acid

•

Sodium Hydroxide

 

Procedure:

 

1.    Read the label on each chemical and record the following:

 

If some of the information is not on the label for the chemicals you choose, the information can be found when you do part 2 or part 5.

 

a.    Name of the compound

 

b.   Molecular formula of the compound

 

c.    CAS number

 

d.   Hazards and safety information (summarize)

 

2.    Using the CRC “Handbook of Chemistry and Physics” and/or the “Merck Index”, which are available in the reference book section of the SMU Library or in the CHEM lounge (CRC does not refer to our Copy and Resource Center.), look up each chemical and determine:

 

a.    Its density

 

b.   Its solubility in various solvents

 

c.    Its boiling and melting points

 

d.   Its “LD 50 (Lethal Dose for 50% of population)

 

3.    Using the “Guidebook for Hazardous Materials” (on reserve in the library or online), look up each chemical and very briefly summarize the handling procedures for a “spill.”

 

4.    Using the “TVLs and BEIs” handbook (on the table in the CHEM lounge), determine the “TWA” (Time Weighted Average), “STEL” (Short Term Exposure Limit) values for each substance. Rank your chemicals from the most hazardous (#1) to the least hazardous (#3).

 

5.    “SDS” = “Safety Data Sheet.” Using an on-line search engine, find a site on the web that has SDS’s for your chemicals. Examine the SDS for each chemical and find any interesting/important “toxicity” or health information as it might relate to exposure to the chemical in the workplace. What information does the SDS give you that the other sources you’ve looked at do not provide?

 

CHEMISTRY 145L                                                                                                            SPRING 2018

 

6.    Chemicals at home:

 

a.    Look around your home, apartment, dorm room, etc. and read the label on some household chemicals, cleaning supplies, and foods.

b.   List all the materials you find that contain one or more of your “target” chemicals.

 

c.    If you find nothing containing the chemicals, list a few of the “interesting” ingredients in the substances in your home.

 

This exercise may seem like “busy work,” but the information you gain today and an understanding of the means by which you gain this information will be very useful to you in the future. Also, the successful completion of this lab will probably give you a better idea of what those tanker trucks that you pass on I-5 are carrying (it isn’t all milk and gasoline!).

 

The goal of this exercise is for you to become familiar with the resources listed, so you should obtain the information from the source listed. It will be assumed for the practicum that you can sit down with one of these references and efficiently find the information you are after.

 

Note: The write-up for this lab MUST be written in your lab notebook.

chemistry 145 Lab 1
14547

CHEMISTRY 145L                                                                                                            SPRING 2018

 

Lab 1: Scientific Measurements & Introduction to the Lab

 

Introduction

 

This lab will introduce you to the lab in which you will be working this semester. You will also become familiar with the correct way to make a measurement in the chemical laboratory, including the use and manipulation of common units, and how chemists indicate their degree of (un)certainty. You will learn about significant figures, and how to manipulate them, and perform some simple calculations to practice the above skills.

 

Background

 

Along with qualitative observations, some of the most important data that chemists collect is in the form of quantitative measurements. When chemists in different labs want to compare results, it is important that the quantities are comparable. To facilitate this, we work in the metric system, report units (always!) and are very intentional about the way we record and report data.

 

When you are making a scientific measurement, you should utilize all of the accuracy which can be obtained from the instrument you are using, and results should be reported to reflect this level of accuracy. Results of calculations using these measurements should also reflect the accuracy of the measurements and the subsequent impact on any calculations. In order to accomplish this, simple rules regarding significant figures (which tell another scientist which numbers are meaningful) should be followed. In this experiment, significant figures will be introduced and emphasized. We will also practice this some in lecture, and you should be mindful of significant figures (sig figs) in all of your work for this course.

 

The Metric System

 

If you’re not familiar with the metric system, more detail can be found on pages 12-16 of your Brown and Holme text. A brief introduction of the pieces relevant to this lab is given here.

 

The metric system is based on the units of meter for length, gram for mass, and liter for volume. Prefixes may be added to indicate multiples in base 10 of these units, which allows use of the same scale to describe very large and very small quantities. Common prefixes include kilo- (1000 units, there are 1000 meters in a kilometer), centi- (0.01 units, there are 0.01 meters in a centimeter, but it can be easier to remember this as 100 centimeters in a meter), milli- (0.001 units- there are 0.001 liters in a milliliter, but this can be easier to remember as 1000 milliliters per liter), and micro- (0.000001 units or 10-6 units, there are 10-6 meters in a micrometer, but this can be easier to remember as 106 micrometers in a meter.) Both ways of thinking of the units are pointed out here, because you always want to stop and make sure your units make sense when converting them for comparison. You probably know from life experience that a centimeter is smaller than a meter; it should make sense to think that there are 100 centimeters per meter. Keeping this type of perspective can make the metric system easier to manipulate until it becomes more familiar. In lab, you should use the prefix that is appropriate for the scale of your measurement. For example, if you have a penny that weighs 3.164 g, you should report it as such, rather than 0.003164 kg (kilograms) or 3164000 µg (micrograms), though all three technically represent the same mass.


 

 

 

1


CHEMISTRY 145L                                                                                                            SPRING 2018

 

Precision of Measurement and Significant Figures

 

The precision of your measurement depends heavily on the instrument that you are using. As a rule of thumb, the markings given on the instrument are known, and you should estimate one place beyond the markings. However, you may ONLY estimate the final digit. If the measurement appears to fall exactly on the line, you can estimate the final digit as zero. This zero is still meaningful, as we will see. This is demonstrated in Figure 1, where the same item is measured on two different rulers.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

https://sites.google.com/site/ivytechchemistry/lab-1

 

Figure 1. The same measurement made with two different rulers.

 

Using metric ruler “A”, you can tell for certain that the object falls between 12 and 13, but you have to estimate the next digit. It appears to be about halfway, but it might be closer to 0.6 than 0.5; the decimal place cannot be reported with certainty. However, we should report it because we know it’s NOT 12.0 or 12.1. We know something about the value, so we can report a significant digit, acknowledging that there is some uncertainty. In the case of ruler A, this would be indicated by recording a value of 12.5 +/- 0.1 cm. Notice the value includes only numbers that are significant, as many significant digits as possible, a measure of the uncertainty of the value, and units. This should be the case for every measurement you record in your notebook!

 

Following the same reasoning for ruler “B”, we now have more markings, which will allow us to report the measurement with greater precision. A closer view of ruler B appears in Figure 2. Here, we can see that the end of the item is quite close to the fifth marking between the 12 and 13, perhaps even right on the line. If the measurement appears to fall exactly on the line, you can estimate the final digit as zero. This zero is still meaningful, and it tells anyone using your data that the measurement was quite close to the line. While it may not be exactly

 

zero, you know it was not half way to the next line!  Figure 2. A closer look at ruler B.


 

2


CHEMISTRY 145L                                                                                                            SPRING 2018

 

Again, you should report that your uncertainty is in the last recorded digit. Thus, you would reflect the greater level of precision by recording this measurement as 12.50 +/- 0.01 cm. 12.50 +/- 0.02 may also be appropriate here, depending on how confident you are in your measurement. Do you believe you could tell the difference between 12.50 and 12.52 cm in this image?

 

When a measurement is recorded as described above, all of the reported numbers have meaning, or are significant, and there is uncertainly only in the final digit. Likewise, when you see a value correctly reported, you can assume that every number is meaningful, and that the uncertainty is in the final digit. It is important to note that when using a digital instrument for a measurement, this same rule is followed. There is some uncertainty in the last number displayed, but it is significant, and all numbers should be recorded.

 

Sometimes, it is necessary to further manipulate your raw data, and it is important to consider the number of significant figures when doing so. The method of handling them depends on what you are doing. For this course, we will limit our discussion to two different possibilities: addition/subtraction and multiplication/division.

 

Let us begin with the first scenario. First, when you are adding and subtracting values, all of the values must have the same units. It should make sense to you that 4 L minus 1 mL is not 3! To see where we go from there, let’s consider a specific example. Say you were interested in a total volume of water from three separate measurements. The first measurement was 234 mL, which was read in a graduated cylinder to +/- 1 mL and contains 3 significant figures. The second and third measurements were made in a slightly more precise graduated cylinder that allowed you to estimate the first decimal place. They were 21.5 and 1.7 mL, with an uncertainty of +/- 0.1 mL, and contain 3 and 2 significant figures respectively. In this example, all of the values are reported with the same units, so we can combine the volumes, but let’s consider the values in liters, as well:

 

 

234   mLor

0.234

L

 

 

21.5 mL

0.0215

L

 

 

1.7 mL

0.0017

L

 

 

257.2 mL

 

0.2572

L

 

 

 

 

 

 

Rounds to

257 mL

0.257 L

 

 

           

 

Here, it is important to note that the uncertainty in the initial measurement was +/- 1 mL. Thus, our overall volume is only certain to the mL. Therefore, we round to the nearest mL. When adding and subtracting values, your answer is certain only to the number of decimal places in your least certain value.

 

Note also, that while the two values, while they appear to be different at a first glance, represent the same volume reported to the same number of significant digits. Without using scientific notation, there is no way to report this value in liters without that initial zero - it is simply a placeholder. Thus, both reported values have three significant digits. Converting 0.257 L into scientific notation yields 2.57 x 10-1, confirming that there are three significant


 

3


CHEMISTRY 145L                                                                                                            SPRING 2018

 

figures (this is one of the strengths of scientific notation). When you see a zero at the beginning of a number, it is not significant.

 

For further example, consider the following:

 

 

10.1

mm

or10.1

mm    or

0.0101

m

0.105

m

105

mm

0.105

m

1.284

cm

 

12.84 mm

0.01284 m

 

Cannot be added

 

127.94 mm

 

0.12794 m

 

as written

 

 

 

 

 

 

Rounds to

 

 

128 mm

 

 

0.128

m

                 

 

When multiplying and dividing, the rules are slightly different. Rather than considering the number of decimal places, we consider the number of significant figures in our least precise value. When multiplying or dividing, report your answer with the same number of significant figures as your least precise starting value.

 

You should also be aware of units, but they need not necessarily match. Units that do match may cancel out, and you should do so when you are able, but they can be carried forward with the number if that is not the case. For example:

 

 

 

 

 

 

 

 

 

 

 

 

Here,   the   units   would   have   been

 

 

 

 

 

 

 

 

 

 

 

 

 

(g•mL)/mL.  Because  mL  appears  on

 

 

(0.825 g/mL)(12.5 mL) = 10.3 g

 

 

 

 

both  the  top  and  bottom,  it  may  be

 

 

 

 

 

 

cancelled to give g as the final answer.

 

 

 

 

 

 

 

 

 

 

 

 

 

Both   values   had   three   significant

 

 

 

 

 

 

 

 

 

 

 

 

 

figures,  leading  to  three  in  the  final

 

 

 

 

 

 

 

 

 

 

 

 

 

answer.

 

 

 

 

 

 

 

 

 

 

 

 

 

Sometimes,  the  units  are  so  different

 

 

 

 

 

 

 

 

 

 

 

 

 

that  none  cancel,  and  they  are  all

 

 

 

 

 

 

 

 

 

 

 

 

 

carried forward. The least precise of the

 

 

 

 

 

 

 

 

 

 

 

 

 

starting  values  have  three  significant

 

 

 

 

 

 

 

 

 

 

 

 

 

figures, so the answer is again reported

 

 

 

22.4

(1.00    )

= 0.0820

 

 

 

 

 

 

with three significant figures (recall that

 

 

(1.00   )(273.15  )

 

the leading zeroes are not significant,

 

 

 

 

and  we  will  discuss  terminal  zeroes

 

 

 

 

 

 

 

 

 

 

 

 

 

shortly).

 

 

52.4×

40.0

×

 

60.0

 

In   other   cases,   multiplication   and

 

 

 

 

division can occur over many steps to

 

 

 

 

intentionally cancel the units. Here, the

 

 

 

 

final units would have been mL g2/ mL

 

 

 

 

g, but this is simplified to cancel when

 

 

1000.

 

40.0

possible  to  leave  only  g  in  the  final

 

=

 

 

 

 

answer. Note the strange decimal at the

 

 

 

3.14

 

 

 

 

 

 

end of 1000.  That tells us something

 

 

 

 

 

 

 

 

 

about those zeroes, and we will discuss

 

 

 

 

 

 

 

 

 

 

 

 

 

that shortly.

 

Let’s revisit zero for a moment. When considering a properly reported number, any non-zero digits are significant, but (as demonstrated in the last set of examples) zero has some nuances you should be aware of.


 

4


CHEMISTRY 145L                                                                                                            SPRING 2018

 

       As noted before, leading zeroes are not significant.

 

       Zeroes occurring in the middle of a number are always significant.

       Trailing zeroes may or may not be significant. Trailing zeroes after a decimal place are always significant. Thus, 1.000 L has 4 significant figures. You should recognize from the discussion of measurement that those trailing zeroes would not have been recorded unless the precision of the instrument allowed it; they are meaningful. When converting that number to mL, though, it gets tricky because trailing zeroes with no decimal place are not significant. Thus, writing 1000 mL would imply that we only knew that value to one significant figure, which was not the case! Thus, we would use a decimal place to indicate that those zeroes were significant, and write 1000. mL as shown in the example above.

 

Trailing zeroes prior to a decimal place are significant, so this notation correctly conveys that we have 4 significant figures in that value.

 

For more examples, a summary of the rules, and practice problems regarding significant figures, see pages 16-18 in your text.

 

Experimental Procedure:

 

Part I: Get to know your lab and safety equipment!

Provide a full page sketch of the lab, indicating the location of the following (you may work in small groups or teams to explore and find these items):

 

Eye washes                                                  Fire blanket

 

Fire extinguishers                                       Sinks

First aid kit                                                     Fume hoods

Emergency showers                                   Emergency numbers

 

Glassware closet                                         Goggles

 

Part II: Measure the linear dimensions of your notebook.

 

You will use both English and metric units to calculate the volume of your lab notebook and compare the two. To accomplish this, obtain the dimensions of your lab notebook in both metric and English units. You should enter this date in your notebook using a table similar to the following:

 

English

Metric

Length

 

Width

 

Thickness

 

 

Remember units and significant figures! The metric measurements should be in centimeters, and the English in inches.

 

Part III: Sugar!

 

You will measure the volume and mass of a single sugar cube in order to determine its density and perform some calculations. The density of an object is its mass per unit volume (d=m/V)


 

5


CHEMISTRY 145L                                                                                                            SPRING 2018

 

and can be obtained through simple measurements. This will require that you measure the length of the three dimensions and use a balance to obtain the mass. Record all data in your notebook for use in future calculations.

 

Part IV: Density of a metallic solid

 

For part IV, you will find the density of a metallic solid by two different methods, compare the two, and attempt to identify the metal with this information. Start by recording the mass of your metal rod, which will be needed for both methods. Make any observations on the rod that may help you to identify it as part of your post-lab.

 

Method 1: Measure the dimensions to find the volume. Recall that the volume of a cylinder is describedπ by V= 2h.

 

With a ruler, measure the length of the rod five times, adjusting it slightly each time to compensate for irregularities in the length.

Again using a ruler, measure the diameter of the rod five times by a similar method.

 

Method 2:  Find the volume by the water displacement method.

 

Fill a small graduated cylinder partway with water, leaving enough space for the water to rise when the rod is added. Record the initial volume of water in the graduated cylinder. Add the metal rod to the cylinder, and record the final volume in the cylinder. The difference in these values (Vf – Vi) is the volume of the rod.

 

Before you leave the lab: Calculate the volume of the metal rod by each method (this is also listed below). Report those values, as well as the mass of the rod, in the spreadsheet open in lab. Your post-lab will require you to access the class data (that will be posted on the course Moodle) to answer some questions. Because your contribution to the class data is vital, a small portion of your grade for this lab will be attached to doing so!

 

Calculations:

 

You may find the useful relationships on the inside of your text to be particular useful for this activity.

Calculate the following in your notebook from your data, report the correct number of significant figures, and show your work:

 

The volume of the book in cubic centimeters.

 

The volume of the book in cubic inches.

The volume of the book in gallons.

 

The volume of the book in liters.

 

The volume of a sugar cube in mL.

 

The density of a sugar cube in g/mL.

 

The number of sugar cubes in one pound of sugar.

 

Start by calculating the average height and diameter of your rod.

 

Using the average height and diameter you’ve calculated, determine the volume of the metal rod.


 

6


CHEMISTRY 145L                                                                                                            SPRING 2018

 

Using the volume measurement you trust the most (you should defend this choice in your discussion), calculate the density of the metal rod.

 

REMEMBER TO CONSULT THE LAB EXPECTATIONS AND COMPLETE ALL PORTIONS OF THE POST-LAB!

 

Post-lab questions:

 

1.    Access the class data for this lab on the Moodle for this course. Which method seemed to provide the most consistent results.

 

2.    Use the calculated value of the rod’s density to suggest any possible substance of which the rod might be composed. Does it make a difference if you use the class data or your own? Which would you deem more reliable? Why?

 

3.    What is the most likely element that was used to make the rod? Defend your answer.

 

Hint: Tables of densities are available online through a variety of sources, but you should cite whichever one you use to answer this question.


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7

CHEMISTRY 145L chemistry lab
14546

CHEMISTRY 145L chemistry lab
14515

Write a research paper about one element from the periodic table of the elements. Select an element that you find interesting and tell the story of that element. In doing so, explain how the element relates to the elements around it in the periodic table and why the element is in that particular location on the table of elements. Below is a list of aspects to explain in the paper: •Who discovered your selected element •When it was discovered •Modern and ancient uses of the element •Ways in which the element’s use impacts our daily lives •Ten (10) physical properties •Ten (10) chemical properties  Requirements   Your paper should be at least 3 pages long with at least 750 words. The paper should have a title page, the body of the paper, and a bibliography of sources. Use at least four reputable sources, which can include scientific journals, popular press, and one Internet source. Write your paper in a Word document in APA format.

Write a research paper
14070 Lab report for chemistry Chemistry lab
13831

3 chapters of sapling homework on general chemistry, i have started all three and completed 51% of the first assignment,31.2% on the second assignment and 27.5 of the third assignment. The homework is due by 6:00 pm 10/20/16

 

if you're willing to do the homework then i'll send you my login information.

chemistry sapling homework
7533

assss

testttt

©2016 Web Design And Development by TrendPro Systems Limited Teach online | Contact us