1. Key
GENERAL CHEMISTRY-II (1412)
S.I. # 2
1. Write the equation for the ideal gas law.
PV = nRT
2. The density of __________ is 0.900 g/L at STP.
a. CH4 b. Ne c. CO d. N2 e. NO
16g 20.18g 28g 28g 30g
D = m/V 0.900 = m/22.4L  m = (.9)(22.4L) = 20.18 B
3. The molecular weight of a gas is _____________g/mol if 3.5g of the gas occupies
2.1L at STP.
Derivation of formula
PV=nRT & n=m/Mw
N=(PV)/(RT)
m/Mw=(PV)/(RT) => Mw=m(PV)/(RT)
Mw= (RT)mg/(PV)
Mw= [(.0821L*atm*mol-1K-1)*(273K)*(3.5g)]/[(1atm*2.1L)]
Mw=(78.45L*atm*mol-1*g)/ (2.1atm*L)= 37 gmol-1 (gmol-1=g/mol)
or
M = (dRT)/P d = 3.5g/2.1L = 1.66 g/L
M = [(1.66)(.0821)(273.15)] / 1 atm = 37 g/mol
4. A gas will be have most like an ideal gas under conditions of ______________
_________________ and __________________ __________________.
High temperature and low pressure.
5. Which gas will deviate the least from ideal behavior?
a. Ne b. CH3Cl c. Kr d. CO2 e. F2
the lightest will deviate from ideal least. A
6. The density of ammonia gas in a 4.32L container at 837 torr and 45°C is
_____________g/L.
PV = nRT n = PV / RT NH3 = 17g
P = 837 toor/760torr = 1.10 atm n = (1.10)(4.32) / (0.0821)(318)
V = 4.32L n = 0.182 mol NH3
n=? (0.182mol NH3) (17g NH3) = 3.1g NH3
R = 0.0821 ( 1 mol)
T = 45°C = (45 + 273) = 318K D = m/V  3.1 g/4.32L = 0.717g/L

2. Key
7. The reaction of 50 mL of Cl2 gas with 50 mL of C2H4 gas via the equation:
Cl2 (g) + C2H4 (g)  C2H4Cl2 (g) will produce a total of __________mL of
product if pressure and temperature are kept constant.
50 mL because the ratio is 1:1:1
8. The effective molar mass is a weighted average of the molar masses of a
mixture’s components. If air at STP has a density of 1.285 g/L, its effective molar
mass is ___________g/mol.
M = dRT / P
d = 1.285 g/L M = [(1.285)(0.0821)(273)] / 1 = 28.8 g/mol
R = 0.0821
T = 273.15 K
P = 1 atm
9. The volume of HCl gas required to react with excess magnesium metal to
produce 6.82L of hydrogen gas at 2.19 atm and 35°C is _______________L.
2 HCl (g) + Mg(s) H2 + MgCl2
it takes twice as much HCl gas as Mg solid to perform the rxn from balancing
equation : 6.82 x 2 = 13.6 L
10. What volume of O2 gas at 25°C and 1 atm pressure is produced by the
decomposition of 7.5g of KClO3 (s)?
PV = nRT V = nRT/P 2 KClO3  3 O2 + 2 KCl-
P = 1 atm V = (0.061)(0.0821)(298) / 1 = 1.5 L
V=?
n = 7.5g / 122.2g x 1 mol = 0.061 mol KClO3
R = 0.0821
T = 25 + 273 = 298K (1.5L)(3 mol O2) / (2 mol KClO3) = 2.2 L O2
11. In a gas mixture of He, Ne, and Ar with a total pressure of 8.40 atm, the mole
fraction of Ar is ____________ if the partial pressures of He and Ne are 1.50 and
2.00 atm respectively.
PT = PHe + PNe + PAr  PT – PHe – PNe = PAr
PHe = 1.50 atm 8.40 – 1.50 – 2.00 = 4.9
PNe = ? partial pressure of Ar = 4.9 atm / 8.4 atm = 0.583atm
PAr = 8.40 atm

3. Key
12. Of the following gasses, ________ will have the greatest rate of effusion at a
given temperature.
A. HBr B. NH3 C. HCl D. CH4 E. Ar
D. CH4 – the lightest
13. An Ideal gas differs from a real gas in that the molecules of an ideal gas have?
no attraction for one another