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Practice - Exam 1

The document is a practice exam for Chemistry 121, Fall 2006, containing various types of questions including true/false, multiple choice, and calculation problems related to chemical reactions and properties. Students are required to show their work and provide answers with the correct number of significant figures. Topics covered include balanced reactions, the law of multiple proportions, and calculations involving moles and mass of compounds.

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32 views4 pages

Practice - Exam 1

The document is a practice exam for Chemistry 121, Fall 2006, containing various types of questions including true/false, multiple choice, and calculation problems related to chemical reactions and properties. Students are required to show their work and provide answers with the correct number of significant figures. Topics covered include balanced reactions, the law of multiple proportions, and calculations involving moles and mass of compounds.

Uploaded by

tyutenovk
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Fall 2006 Chemistry 121 Practice Exam 1

Name _________________________________ Section: ⎕ 9:10 am ⎕ 11:10 am


For each of the questions below, your answer should be given in the appropriate
number of significant figures.
Show your work for all problems. Credit will only be given when work is shown.

For the following true/false questions, indicate whether the statement is true or false. If the
statement is false, correct the statement.
1. (10 pts) In a balanced reaction, the sum of the coefficients for the reactants always
equals the sum of the coefficients of the products.

2. (10 pts) In a balanced reaction, the total moles of reactants equals the total moles of
the products.

For questions 3 and 4, circle the most appropriate answer and then briefly explain why
you chose that answer.
3. (10 pts) Which of the following pairs of compounds can be used to illustrate the law
of multiple proportions?
a. NH4 and NH4Cl
b. ZnO2 and ZnCl2
c. H2O and HCl
d. NO and NO2
e. CH4 and CO2
4. (10 pts) If a reaction vessel contains equal masses of Fe and S, the mass of FeS
that can theoretically be produced according to the reaction:
Fe (s) + S (s) Æ FeS (s)
a. Equals the sum of the masses of Fe and S
b. Is greater than the sum of the masses of Fe and S
c. Is less than the sum of the masses of Fe and S

5. (10 pts) A sample of ammonia, NH3, contains 4.5 x 1019 hydrogen atoms. How
many NH3 molecules are in this sample?

How many moles of NH3 are present in this sample?


6. (8 pts) Manganese makes up 1.3 x 10-4 % by mass of the elements found in a
normal healthy body. How many grams of manganese would be found in the body
of a person weighing 183 lb (2.2 lb = 1.0 kg)?

7. (12 pts) Their names suggest that the law of definite proportions and the law of
multiple proportions are incompatible. Explain why they are not incompatible. You
may wish to illustrate your point using compounds as examples.

8. (8 pts) One way of preserving vegetables or meats is to soak them in a brine (or salt
water) solution. If a solution is made by dissolving 532 g of NaCl in enough water to
make 1.50 L of brine, what is the molarity of the solution?
9. (12 pts) Cisplatin, Pt(NH3)2Cl2 is an antitumor agent. How many grams of cisplatin
can be produced from 1.00 kg of platinum?

10. (10 pts) A sample of sodium bicarbonate (baking soda) was found to consist of
9.122 g Na, 0.4000 g H, 4.766 g C, and 19.04 g O. Calculate the moles of each
element present, and determine the empirical formula for sodium bicarbonate.

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