Name: ________________________
Hour: ____ Date: ___________
Chemistry: Graham’s Law
Do the following problems, showing your work and including all proper units.
1. If neon gas travels at 400 m/s at a given temperature, calculate the velocity of butane, C4H10, at the same
temperature.
2. Hydrogen sulfide, H2S, has a very strong rotten egg odor. Methyl salicylate, C8H8O3, has a wintergreen odor,
and benzaldehyde, C7H6O, has a pleasant almond odor. If the vapors for these three substances were
released at the same time from across a room, which odor would you smell first? Show your work and
explain your answer.
3. A nitrogen molecule travels at about 505 m/s at room temperature. Find the velocity of a helium atom at the
same temperature.
4. A carbon dioxide molecule travels at 45.0 m/s at a certain temperature. At the same temperature, find the
velocity of an oxygen molecule.
5. Nitrogen gas effuses through an opening 1.59 times faster than does an unknown gas.
a. Calculate the molecular mass of the unknown gas.
b. Make a reasonable prediction as to what the unknown gas is.
6. An unknown gas diffuses 1.62 times slower than does oxygen gas.
a. Calculate the molecular mass of the unknown gas.
b. Make a reasonable prediction as to what the unknown gas is.
Answers:
1.
2.
3.
236 m/s
H2S
1336 m/s
4.
5a.
5b.
52.8 m/s
71 a.m.u.
Cl2
6a.
6b.
84 a.m.u.
Kr
KEY
Chemistry: Graham’s Law
Do the following problems, showing your work and including all proper units.
1. If neon gas travels at 400 m/s at a given temperature, calculate the velocity of butane, C 4H10, at the
same temperature.
Neon
m2
20.2 g
v2
400 m/s
Unknown
m1
58 g
v1
? m/s
v1
v2
m2
m1
v1
400 m/s
20.2 g
58 g
v1
236 m/s
2. Hydrogen sulfide, H2S, has a very strong rotten egg odor. Methyl salicylate, C8H8O3, has a wintergreen odor,
and benzaldehyde, C7H6O, has a pleasant almond odor. If the vapors for these three substances were
released at the same time from across a room, which odor would you smell first? Show your work and
explain your answer.
H2 S 34 amu
C 8 H8 O 3
C 7H6 O
152 amu
106 amu
All substances have the same kinetic energy (all are at the same temperature).
Therefore, the lightest molecules will move fastest.
3. A nitrogen molecule travels at about 505 m/s at room temperature. Find the velocity of a helium atom at the
same temperature.
N2
m2
28 g
v2
505 m/s
Helium
m1
4g
v1
? m/s
v1
v2
m2
m1
v1
505 m/s
28 g
4g
v1
1336 m/s
4. A carbon dioxide molecule travels at 45.0 m/s at a certain temperature. At the same temperature, find
the velocity of an oxygen molecule.
CO 2
O2
m2
44 g
v2
45 m/s
m1
32 g
v1
? m/s
v1
v2
m2
m1
v1
45 m/s
44 g
32 g
v1
52.8 m/s
5. Nitrogen gas effuses through an opening 1.59 times faster than does an unknown gas.
a. Calculate the molecular mass of the unknown gas.
Nitrogen
Unknown
m2
v2
28 amu
1.59 x
m1
58 amu
v1
1x
v1
v2
m2
m1
1.59 x
1x
m2
28 g
b. Make a reasonable prediction as to what the unknown gas is.
Chlorine gas, Cl2
2 Cl @ 35.453 amu = 70.9 amu
m2
70.8 amu
KEY – Page 2
Chemistry: Graham’s Law
6. An unknown gas diffuses 1.62 times slower than does oxygen gas.
a. Calculate the molecular mass of the unknown gas.
Oxygen
m1
32 amu
v2
1.62 x
Unknown
m2
? amu
v2
1x
v1
v2
m2
m1
1.62 x
1x
m2
32 amu
m2
b. Make a reasonable prediction as to what the unknown gas is.
Krypton, Kr
Answers:
1.
2.
3.
236 m/s
H2S
1336 m/s
molecular mass is 83.80 amu
4.
5a.
5b.
52.8 m/s
71 a.m.u.
Cl2
6a.
6b.
84 a.m.u.
Kr
84 amu