Name _________________________________
CHAPTER 10 PRACTICE TEST
Period ____ Date ___________ Seat ________
A. Matching
Match each description in Column B 5to the correct term in Column A. Write the leter of the correct
description on the line.
Column A
Column B
________ 1. Atomic mass
a. the volume occupied by a mole of any gas at STP (22.4L)
________ 2. Empirical formula
b. describes the actual number of atoms of each element
in the molecule of a compound.
________ 3. Molar volume
c. 0° C and 101.3 kPa
________ 4. Avogadro’s number
d. the mass of a mole of a substance
________ 5. Standard temperature
and pressure (STP)
e. The number (6.02 x 1023) of representative particles in a
one mole of a substance
________ 6. Molecular formula
f. the percent by mass of each element in a compound
________ 7. Molar mass
g. the formula that gives the lowest whole-number
ratio of the elements in a compound.
_______
h. the mass in amus of an atom of an element
8. Percent composition
B. Multiple Choice
Choose the best answer and write up its letter on the line.
_______
9.
One mole of representative particles in a molecular compound is equal to
a. one formula unit
c. 22.4 liters at STP
b. 6.02 x 1023 atoms
d. 6.02 x 1023 molecules
_______
10. How many carbon atoms are in 4 molecules of ethanol (C2H6O)?
a. 2
c. 8
23
b. 8 x (6.02 x 10 )
d. 2 x (6.02 x 1023)
_______
11. The chemical formula of Epsom salt is MgSO4. What is the molar mass of Epsom salt?
a. 24.3 g
c. 64.0 g
b. 32.1 g
d. 120.4 g
_______
12. The molar mass of ribose (C5H10O5) is 150 g. What is the mass of 0.25 mol of ribose?
a. 600 g
c. 1.7 x 10-3
b. 37.5 g
d. 75 g
_______
13. What is the volume (in liters at STP) of 4.0 mol of laughing gas, N2O?
a. 0.18 L
c. 5.6 L
b. 89.6 L
d. 11.0 L
1
CHAPTER 10 PRACTICE TEST
_______
14. How many representative particles are in 0.300 mol of acetaminaphen (C8H9NO2)?
a. 2.01 x 1024 molecules
c. 1.81 x 1023 molecules
b. 4.98 x 10-25 molecules
d. 0.300 molecules
_______
15. How many moles are in 11.2 L of chlorine gas at STP?
a. 0.50 mol
c. 2.00 mol
b. 250.9 mol
d. 11.2 mol
_______
16. The density of a diatomic gas at STP is 1.25 g/L. What is the name of the gas?
a. Hydrogen (H2)
c. Nitrogen (N2)
b. Chlorine (Cl2)
d. Oxygen (O2)
_______
17. The molar mass of molecular oxygen (a gas) is
a. 16.0 g
b. 32.0 g
c. equal to the mass of one mole of oxygen atoms.
d. none of the above
_______
18. At STP, 1 mole each of hydrogen, oxygen, nitrogen, and fluorine gas:
a. contain twice Avogadro’s number of representative particles.
b. have the same densities.
c. occupy different volumes.
d. occupy the same volumes.
_______
19. A party balloon filled with helium has a mass of 2.0 g at STP. Which expression
should be used to find the volume of helium in the balloon?
a.
1 mol
2.0 g
22.4 L
X
X
4.0 g
1
1 mol
c.
b. 22.4 L X 4 g He
1 mol
1
d.
2.0 g
4 g He
1 mol
X
X
22.4 L 1 mol
1
1 mol
22.4 L
X
4 g He
1
_______
20. The molar mass of a gas can be determined from:
a. Avogadro’s number.
c. the density of the gas at STP
b. the volume of a mole of the gas.
d. none of these.
_______
21. What is the percent by mass of carbon in ethane (C2H6)?
a. 100%
c. 80%
b. 20%
d. 24%
_______
22. Which of the following is not an empirical formula?
a. NH3
c. C5H10O5
b. C2H8O
d. NH4Cl
2
CHAPTER 10 PRACTICE TEST
_______
23. What expression represents the percent by mass of carbon in methane, CH4?
a.
1g
16 g
X 100
c.
16 g
12 g
X 100
b.
16 g
4g
X 100
d.
12 g
16 g
X 100
_______
24. A compound has the empirical formula CH2 and a molar mass of 56.0 g. What is its
molecular formula?
a. C4H8
c. C3H6
b. CH2
d. C5H10
_______
25. Ribose (C5H10O5) and acetic acid (C2H4O2) share the same empirical formula, which is:
a. CHO
c. CH2O
b. CHO2
d. C2HO
C. Problems
Solve the following problems in the space provided. For problems 26 and 27, show your work, include
the units, and circle the answer. Assume all volume problems are at STP.
26. Find the mass, in grams, of 3.01 x 1023 atoms of Nitrogen (N). (5 points)
27. Find the volume, in liters, of 100.0 g of molecular oxygen (O2). (5 points)
28. Find the molecular formula for caffeine. The molar mass is 194 g/mol and the empirical is
C4H5N2O. (5 points)
3
CHAPTER 10 PRACTICE TEST
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
H
G
A
E
C
B
D
F
D
C
D
B
B
14.C
15.A
16.C
17.B
18.D
19.A
20.C
21.C
22.C
23.D
24.A
25.C
26. Mass of C =
3.01 x 1023 atoms of N
1 mol of N
X
X
1
6.02 x 1023 atoms of N
=
27.
Volume of N2
14.0 g of N
1 mol of N
7.0 g
=
=
100.0 g O2
1
X
1 mol of O2
32 g O2
X
22.4 L O2
1 mol of O2
70.0 L
28. Step 1: Find the molar mass of the empirical formula, C4H5N2O
C4
H5
N2
O
= 12.0 g x 4
= 1.0 g x 5
= 14.0 g x 2
= 16.0 g x 1
C4H5N2O
=
=
=
=
=
48.0 g
5.0 g
28.0 g
16.0 g
97.0 g
Step 2: Determine the molar mass multiplier by dividing the molar mass of Caffeine by the molar
mass of the empirical formula.
Molar mass of caffeine
Molar mass of empirical formula
194 g
97 g = 2
Step 3: Multiply the multiplier through the empirical formula.
2 x C4H5N2O = C8H10N4O2
Problems 10 – 16 worked out on page 5.
4
CHAPTER 10 PRACTICE TEST
10. If there are 2 atoms of carbon in one molecule of C2H6O, then there
Are 8 atoms of carbon in four molecules of C2H6O.
11. Find the molar mass Epsom salt, MgSO4.
Mg = 24.3 g x 1
S = 32.1 g x 1
O4 = 16.0 g x 4
MgSO4 =
=
=
=
=
24.3 g
32.1 g
64.0 g
120.4.0 g
12.
Mass of
=
ribose
0.25 mol ribose
1
X
150 g ribose
1.00 mol ribose
= 37.5 g ribose
Volume
=
of N2O
4.0 mol N2O
1
X
22.4 L N2O
1.00 mol N2O
= 89.6 L N2O
13.
Representative particles
14.
(R) Rep.
=
particles
0.300 mol aceto
1
X
Moles of
=
Cl2
11.2 L Cl2
1
X
6.02 x 1023 R aceto
= 1.81 x 1023 R aceto
1.00 mol aceto
15.
1.00 mol Cl2
22.4 L Cl2
= 0.5 mol Cl2
16.
Molar
mass of
diatomic =
gas (dg)
diatomic gas
1.25 g dg
1
X
22.4 L dg
1.00 mol dg
= 28.0 g dg/mol
diatomic means two atoms
28.0 g is the molar mass of the mystery diatomic gas. Divide 28.0 g by 2 to obtain the
monatomic molar mass, which is 14.0 g. Nitrogen (N) has a molar mass of 14.0 g.
5