TTU General Chemistry

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Chem 111 - Quiz 2B - Fall, 1997
Chapter II: Chemical Formulas and Compound Stoichiometry

1. Identify the compound below which is a molecular compound:

a) CaF2
b) NaCl
c) Na2CO3
d) NH4NO3
e) SO3

2. Identify the compound formula that is INCORRECT.

a) AgCl = silver chloride
b) KNO3 = potassium nitrate
c) CuCO3 = copper(I) carbonate
d) NH4Cl = ammonium chloride
e) ZnBr2 = zinc bromide

3. Calculate the formula weight of iron(III) sulfate, Fe2(SO4)3.

a) 351.9
b) 489.8
c) 399.9
d) 344.0
e) 335.0

4. Calculate the % Oxygen by mass in glucose, C6H12O6.

a) 53.3%
b) 3.33%
c) 25.0%
d) 57.5%
e) 5.3 x 10-1%

5. Determine the simplest empirical formula of the drug methaqualone with the following composition by mass: 76.78% C; 5.64% H; 11.19% N; 6.39% O.

a) C12H10N2O
b) C6H6NO
c) C12H10NO
d) C16H14N2O
e) C13HN2O

6. An alkene hydrocarbon with an empirical formula of CH has a molecular weight of 26.0 amu. What is the true molecular formula for the compound?

a) CH
b) C2H2
c) CH2
d) C2H4
e) C3H3

7. Calculate the mass of a single molecule of water in grams.

a) 18.0 x 10-23 g
b) 18.0 g
c) 1.67 x 10-24 g
d) 3.0 x 10-23 g
e) 3.3 x 1022 g

8. How many moles of benzene (C6H6) are present in 7.81 grams of benzene?

a) 7.81 mol
b) 1.00 mol
c) 0.100 mol
d) 78.1 mol
e) 609.9 mol

9. Identify the INCORRECT statement:

a) One mole of water contains 6.022 x 1023 H2O molecules.
b) There are 16.0 g in 1.00 mole of O2.
c) 12.0 grams of Carbon have the same number of atoms as 14.0 grams of Nitrogen.
d) 28.0 grams of N2 have the same number of molecules as 32.0 grams of O2.
e) A mole is the amount of substance having the same number of particles as 12 grams of pure Carbon-12.

10. How many glucose molecules are present in 1.0 picogram (1 trillionth of a gram) of glucose, C6H12O6?

a) 6.02 x 1012 molecules
b) 3.34 x 10211 molecules
c) 6.02 x 1011 molecules
d) 33 molecules
e) 3.34 x 109 molecules

11. Which has a greater mass?

a) 1 atom of iron
b) 1 atom of Neon
c) 1 molecule of carbon dioxide
d) 1 molecule of water

12. In which sample are there more particles?

a) 1.0 gram of gold
b) 1.0 gram of carbon
c) 1.0 gram of helium
d) 1.0 gram of iron

13. The fact that water is always found to be 89% Oxygen and 11% Hydrogen by mass is an example of:

a) The Law of Conservation of Matter
b) The Law of Conservation of Energy
c) The Law of Multiple Proportions
d) The Law of Definite Proportions
e) Democritus' theory of atoms

14. Which of the following species DOES NOT represent an element in its most stable form?

a) H2
b) Br
c) S8
d) P4
e) Ne

15. The number of protons in a silicon atom is:

a) 28
b) 14
c) 32
d) 16
e) 47

KEY

1)e 2)c 3)c 4)a 5)d 6)b 7)d 8)c 9)b 10)e 11)a 12)c 13)d 14)b 15)b

Selected solutions:

Problem 5:
Divide the % composition of each element by that element's atomic weight. That converts a mass ratio to a mole ratio. Then convert that mole ratio to whole numbers by dividing each of the mole ratio numbers by the smallest of the numbers. That gives you 16:14:2:1

Problem 7:
Calculate the mass of a single molecule of water in grams.

18.0 grams of H2O make up 1 mole.
1 mole is 6.022 x 1023 molecules

So: 

      18.0 grams/mol
-----------------------    = 3.0 x 10-23 grams/molecule
6.022 x 1023 molecules/mol