Chem problems

Name _______________________________ Chem 101.01 Fall 2020

Written Assignment #1

This assignment is worth a possible total of 75 points. Place your answer in the space provided. Remember that in the problems you must show ALL your work in writing in order to receive full credit for the answers in Part III. No late papers are accepted except by previous arrangement with the instructor. Submit all assignments through moodle.

This assignment is due on Friday, Oct 2nd, 2020

PART I - True/False - Circle your response. ( 3 pts each , 12 pts total)

1. Upon heating a copper sample will expand, leading to a lower density.

TRUE FALSE

2. If a pure liquid is sealed in a container and heated to vaporize it, then it should weigh

less because the gas is less dense than its liquid. TRUE FALSE

3. There are 1000 nm in a cm. TRUE FALSE

4. The number 0.0540 g has 3 significant figures. TRUE FALSE

PART II - Multiple Choice - Circle your response.* ( 4 pts each, 20 pts total). Note that more than one answer may be needed to answer the question completely for full credit.

1. A solid metal cube has an edge which is 11.4 mm long, and a mass of 6.67 g. What is

the density of the cube? (A cube has all sides of equal length.)

(a) 5.85 g/cm3 (b) 1.71 g/mm3 (c) 4.50 g/cm3 (d) 0.0877 g cm3

2. Which of the following is/are INCORRECT conversions in the metric system? Circle

ALL that are false - there may be more than one! - for a complete answer.

(a) 1 km = 1000 m (b) 50 mL = 0.50 L

(c) 125 mm = 12.5 cm (d) 23 pm = 0.000000000023 m

3. Choose which of the following are examples of a chemical change/reaction, rather than

(only) a physical change. Circle ALL that apply.

(a) Dissolving potassium chloride, a salt substitute, in water.

(b) Seashells “fizz” when dissolved in vinegar.

(c) Fine steel wool can be burned in air.

(d) Pure water freezes at 0 oC

4. A quality control lab measured the % moisture in four samples of raw hamburger

and got the following values: 64.53, 64.45, 65.10 and 64.78. An independent lab

with high-level analytical equipment obtained an average of 65.05% moisture.

In comparing the results of these two labs, choose the statement (s) you agree with:

(a) The difference in the two average values (for the results of the two labs) is less

than 0.05% moistures.

(b) The quality control lab is expected to have a higher level of accuracy than the

other lab.

(c) The quality control lab results seem to give a lower value overall (with one or two

exceptions);i.e., the data may have a systematic error which results in a lower

value than expected.

(d) None of these statements are reasonable.

5. Use the meaning of the prefix "nano-" to select the value of "x" in this equation:

1 m = 1 x 10x nm . The value of " x " is

(a) +9 (b) -6 (c) +6 (d) -9

PART III - Written Response (23 pts total)

This section requires that you SHOW/EXPLAIN YOUR WORK clearly and legibly in order to be eligible for full credit for each question. This means that you write your calculations down in a way that is understandable to an “outside” reader (i.e., someone not taking this course!). Show any equations that you use, like calculations with density ( d = m/v). You must also use the correct number of significant figures. Unless you follow these directions, you will not receive full credit, even though you have the correct answer, numerically speaking!!!!! [See “Guidelines” in Syllabus]

1. ( 8 pts) A European car advertises an efficiency of 22 km/L while an American car

lists 30 mi/gal. Show by calculation which one is more efficient; i.e., convert one

value to the units of the other. Clearly label your units!

2. (6 pts) Consider butter (density = 0.860 g/mL) and sand (density = 2.28 g/mL).

If 1.00 mL of butter were mixed with 1.00 mL of sand and mixed as thoroughly as

possible (!), what would be the density of the resulting mixture?

_______ g/mL

3. (9 pts) In the handout, “Types of Mixtures”, the dimensions of the particles are all given in nanometers as the unit.

(a) Convert 0.3 nm (the size of a small molecule) to inches __________ in

(b) Give an estimate* of the diameter of a grain of beach sand in inches and then convert it to nanometers. estimated value _________ in

converted to _________ nm

(c) Cite your source of information for the diameter : ________________________

4. ( 20 pts) Read the article, “Tattoo Ink Worries” [C&EN, Aug., 22, 2016]. Answer the following questions using complete sentences, or as directed . [Write legibly or type your responses on a separate sheet of paper– if it is illegible, you will not receive credit for the response.]

(a) What are some of the sources (list at least two) of the “repurposed ink used in tattoos?

(b) Describe (1 - 2 sentences) the governmental policies on tattooing (how it is regulated) in the US and Europe.

(c) Besides the risk of infections, there are risks from the chemicals used in the inks.

What is the top chemical of concern (give its family name from the article), what is its effect, and where does it mainly come from?

(d) Besides the ink, there are concerns about the preservatives that are sometimes added to the ink. Describe one of these substances and its effect, as given in the article.

(e) Describe, in your own understanding, what is meant by the “knowledge gap” about this procedure. Use specific information from the article to illustrate your description

(2-3 sentences).

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BONUS: (5 pts) - Show work (as instructed in Part III).

The recommended dose of an asthma drug is given as 6 mg/kg of body mass.

(a) What should the dosage be for a 165-lb person? _____ mg

(b) Comment on the use of significant figures in this case, and how you might think a pharmacist would approach this. Do you think a pharmacist would "round up" for dosages?