Name: ______________________ Class: _________________ Date: _________
ID: A
Moles Pre-Test
True/False
Indicate whether the sentence or statement is true or false.
____
1. The formula of a compound that expresses the smallest whole-number ratio of
the atoms present is called the empirical formula
____
2. The empirical formula and the molecular formula for a compound cannot be the
same
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
____
3. 1 mole of oxygen atoms represents
a. 6.02 x 10^23 atoms
d. 1.00 g
b. 16 atoms
e. None of the above
c. 32.0 g
____
4. Which represents the greatest number of atoms?
a. 50.0 g Zn
d. 50.0 g Cu
b. 50.0 g Al
e. all the same
c. 50.0 g Fe
____
5. Which represents the greatest mass?
a. 1.0 mol Zn
d. 1.0 mol Fe
b. 1.0 mol Cu
e. all the same
c. 1.0 mol Al
1
Name: ______________________
ID: A
____
6. Calculate the molar mass of a sample if a single molecule weighs 5.34 x 10^-23
g
a. 12.0 g/mol
c. 1.13 x 10^46 g/mol
b. 32.2 g/mol
d. 5.34 x 10^-23 g/mol
____
7. Calculate the mass of 20.0 moles of He (in g)
a. 5.00
d. 80.1
b. 1.20 x 10^25
e. 6.02 x 10^23
c. 1.00
____
8. A 20.0 g sample of Ca contains how many calcium atoms?
a. 20.0 atoms
d. 40.1 atoms
b. 6.02 x 10^23 atoms
e. 0.500 atoms
c. 3.0 x 10^23 atoms
____
9. The molar mass of calcium phosphate is
a. 175.13 g/mol
d. 310.18 g/mol
b. 324.99 g/mol
e. none of the above
c. 135.05 g/mol
____ 10. The molar mass of glucose, C6H12O6 is
a. 180 g/molol
c. 29 g/mole
b. 169 g/mol
d. 6.02 x 10^23 g/m
2
Name: ______________________
ID: A
____ 11. The mass in grams of molecular hydrogen (hydrogen gas) is
a. 6 x 10^23
d. 12 g
b. 6.0 g
e. none of the above
c. 12.0 x 10^23
____ 12. How many molecules of O2 are there in 4.0 mol of O2?
a. 1.9 x 10^25
d. 2.4 x 10^24
b. 128
e. 64
c. 6.6 x 10^-24
____ 13. 1 mole of oxygen molecules contains how many moles of oxygen atoms?
a. 1.204 x 10^24
d. 6.02 x 10^23
b. 3.01 x 10^23
e. 32
c. 16
____ 14. Convert 48 g O2 to mole O2
a. 0.75 mol
b. 3 x10^23 mol
c. 1.5 x 10^-23 mol
d. 3.0 mol
e. 1.5 mol
____ 15. Consider separate 100g samples of each of the following: NH3, N2O, HCN, N2H4,
and HNO3. Which of the samples has the LEAST mass of nitrogen?
a. HCN
d. NH3
b. N2H4
e. N2O
c. HNO3
3
Name: ______________________
ID: A
____ 16. The mass percent of oxygen is in CaO is
a. cannot be determined from the d. 25.0%
information given
b. 50%
e. 72.4%
c. 28.5%
____ 17. Vinegar contains carbon, hydrogen, and oxygen with percent masses of 40.01% C
and 6.70% H. If the molar mass of vinegar is about 60 g/mol, what is its
molecular formula?
a. C2H4O2
d. C3H8O
b. CH2O
e. C2H20O
c. C3H7O3
____ 18. A compound has a molar mass of 100g/mol and the percent composition (by
mass) of 65.4 % C, 5.45% H and 29.09% O. Determine the empirical formula and
the molecular
a. CH4O and C3H12O3
d. C3H3O and C6H6O2
b. C3HO and C6H2O2
e. CHO and C6H6O6
c. CH2O and C4H8O4
Numeric Response
19. A sample containing 4.90 mol of Ag has a mass of __________g
4
Name: ______________________
ID: A
20. A 18.4 g sample of Au contains how many atoms?
21. Calculate the percentage composition (by mass) of all the elements in Cd3(AsO4)
22. Determine the percentage composition (by mass) of H2SO4
23. Determine the percentage composition (by mass) of NH4NO3
Short Answer
24. Determine the empirical formula of a compound containing 54.2% F and 45.8%
S(by mass)
5
Name: ______________________
ID: A
25. A compound contains 12.8 % C, 2.1% H, and 85.1% Br (by mass). Calculate the
empirical formula and the molecular formula of the compound given that he molar
mass is 237 g/mol.
6
ID: A
Moles Pre-Test
Answer Section
TRUE/FALSE
1. ANS: T
2. ANS: F
MULTIPLE CHOICE
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
A
B
A
B
D
C
D
A
D
D
A
E
C
C
A
D
NUMERIC RESPONSE
19. ANS:
529
20. ANS:
5.62 x 10^22 atoms
21. ANS:
54.8%Cd, 24.4% As, 20.8% O
1
ID: A
22. ANS:
2.06% H; 32.69% S; 65.25% O
23. ANS:
35.00 % N; 59.96% O; 5.04% H
SHORT ANSWER
24. ANS:
SF2
25. ANS:
Empirical formula = CH2Br;
Molecular formula = C2H4Br2
2