9/25/2014
Which graph represents the relationship of the pressure and temperature of a gas at a constant volume?
Some few elements occur naturally only as single atoms, without combining with or forming bonds to other atoms. Which elements are they? a)
b)
c)
d)
e)
a)
Elements in Group 1, such as hydrogen
Elements in Group 16, such as sulfur
Elements in Group 17, such as chlorine
Elements in Group 18, such as neon
none of the above
T
d) P
T
P
T
PV = nRT, so P = nR
V T. As T ↑, P ↑ in a linear fashion.
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Which of these drawing best represents the arrangement of particles in a gas‐filled container?
a)
b) c) d) Compared to Cl2, an equal number of CO2
molecules at the same temperature
a) has less volume, because the molecules have less mass
b) exhibits greater pressure, because the molecules are moving more quickly
c) has greater volume, because there are more atoms
d) exhibits less pressure, because the molecules are smaller in size
e) none of the above
Gas particles are generally not in contact with one another, are constantly in rapid, random motion, and expand to fill an entire container. In solids and liquids, particles are in physical contact with each other. 2
P
T
c) The Group 18 elements are called the “Noble Gases” for this reason: single, uncombined atoms are always in the gas phase. 1
b) P
PV = nRT holds for any gas or mixture of gases. The nature of the gas has no effect on P or V.
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1
9/25/2014
A balloon has a volume of 0.500L at 25°C and 1 atm
pressure. What happens to the volume if T is increased to 50°C and P to 2 atm? a)
b)
c)
d)
e)
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the volume increases
the volume decreases
the volume stays the same
it depends on the gas in the balloon
it is impossible to say without more information
PV = nRT, so V = nRT/P: P↑ V↓ and T↑ V↑
Which has the larger effect?
P1 = 1 atm, P2 = 2 atm, so P2 = 2P1: so half the V.
T1 = 25+273 = 298K, T2 = 50+273 = 323K, so T doesn’t
double. Overall, V↓ from larger pressure change.
Which gas has the highest density, if at equal pressures? a) N2 at –20°C
b) O2 at –20°C
c) N2 at +20°C
d) O2 at +20°C
e) more information is required to answer
ρ = MM(P/RT), so ρ ↑ when MM ↑ and T ↓
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