Gas Laws 101
An aerosol can contains carbon dioxide as its propellant. If the can has an internal pressure of 1.3 atm at 25.0 *C, what pressure would it have if the temperature were accidentally raised to 450*C? Assume the can hasn't yet burst.
3.15 atm
H2 and F2 react according to the following equation, forming HF.
H2(g) + F2(g) -> 2HF(g); dH* = -271 kJ
If H2(g) and F2(g) were mixed in a thermally insulated vessel, the reaction that occurred would be
a. endothermic, and the temperature of the reaction system would fall
b. We could not tell unless the original and final temperatures were given.
c. exothermic, and the temperature of the reaction system would fall.
d. exothermic and the temperature of the reaction system would rise.
e. endothermic, and the temperature of the reaction system would rise.
D
Calculate the standard enthalpy change for this reaction.
2SO2(g) + O2(g) + 2H2O(g) -> 2H2SO4(l)
SO2(g) dHf* = -296.8 kJ/mol
H2SO4(l) dHf* = -814.0 kJ/mol
H2O(g) dHf* = -241.8 kJ/mol
O2(g) dHf* = 0 kJ/mol
-550.8 kJ
Calculate the rms speed of N2 molecules at 125*C.
595.43 m/s
Calculate the number of molecules in a deep breath of air whose volume is 2.50 L at body temperature, 37*C, and a pressure of 735 torr. Assume the breath is laden with moisture. The vapor pressure of water at 37*C is 47.067 mm Hg.
5.4 x 1022 molecules
A sample of copper absorbs 43.6 kJ of heat, resulting in a temperature rise of 75.0*C. What is the mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J/g*C?
1.5 kg
What volume will be occupied by 25.2 g of CO2 at 0.84 atm and 25*C?
16.7 L
Two metals of equal mass with different heat capacities are subjected to the same amount of heat. Which undergoes the smaller change in temperature?
a. The metal with the higher heat capacity undergoes the smaller change in temperature.
b. Both undergo the same change in temperature.
c. You need to know the initial temperatures of the metals.
d. You need to know which metals you have.
e. The metal with the lower heat capacity undergoes the smaller change in temperature.
A
Use the standard reaction enthalpies given below to determine the dH*rxn for the following reaction:
P4(g) + 10Cl2(g) -> 4PCl5(s) dH*rxn = ?
Given:
PCl5(s) --> PCl3(g) + Cl2(g) dH*rxn = +157 kJ
P4(g) + 6Cl2(g) --> 4PCl3(g) dH*rxn = -1207 kJ
-1835 kJ
Which of the following gases effuses most rapidly?
A. nitrogen
B. ammonia
C. oxygen
D. carbon monoxide
E. hydrogen chloride
B. ammonia
4NH3(g) + 5O2(g) --> 4NO(g) + 6H2O(g)
What volume of oxygen at 35*C and 2.15 atm is needed to produce 50.0 g of nitric oxide.
24.49 L
A 4.98 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb calorimeter with a heat capacity of 4.25 kJ/*C. If the temperature rose from 29.5*C to 69.8*C, determine the value of dH* for the combustion of aniline.
-3201.4 kJ/mole
If a constant number of moles of a gas at 1.35 atm and 205.1 K has a volume of 23.8 L, what will the final volume of the gas be if the pressure change to 2.84 atm and the temperature rises to 233.4 K?
12.88 L
How much heat is liberated at constant pressure if 0.833 g of calcium carbonate reacts with 59.7 mL of 0.251 M hydrochloric acid?
CaCO3(s) + 2HCl(aq) -> CaCl2(aq) + H2O(l) +CO2(g); dH* = -15.2 kJ
0.113 kJ
Use the dH*f and dH* information provided to calculate dH*f for IF:
dH*f (kJ/mol) IF7(g) + I2(g) -> IF5(g) + 2IF(g)
dH*rxn = -89 kJ
IF7(g) -941
IF5(g) -840
I2 0
-95 kJ/mole
22Rank the following gases in order of average molecular speed, giving a "1" to the fastest. Assume they are all at the same temperature.
CO, SF6, H2S, Cl2, HBr
1. CO
2. H2S
3. Cl2
4. HBr
5. SF6
An amount of N2 gas originally held at 4.75 atm in a 1.00L container at 26*C is transferred to a 10.0L container at 20*C. There it is mixed with some O2 gas which was originally held in a 5.00L container at 26*C and 5.25 atm. What is the total pressure in the new container?
3.04 atm
Some chemical cold packs contain NH4NO3 as the active ingredient. When 4.00g of NH4NO3 is dissolved in 96.0g of water, the temperature of the resulting solution is 3.07*C colder than the water and ammonium nitrate were before they were mixed together. What is the value of dH for the following dissolution process? (H2O: 4.184 J/g*C)
NH4NO3(s) --> NH4NO3(aq) dH = ?
25.7 kJ
A 2.56 g sample of a colorless liquid was vaporized in a 250 ml vessel at 121*C and 786 mm Hg. What is the molecular weight of this substance?
320.2 g/mole
At constant pressure and 25*C, what is dH* for the following reaction
2C2H6(g) + 7O2(g) -> 4CO2(g) + H2O(l)
if the complete consumption of 38.2 g of C2H6 liberates 1981 kJ of heat energy?
-3120 kJ
How much energy is required to decompose 765 g of PCl3, according to the reaction below? The molar mass of PCl3 is 137.32 g/mol.
4PCl3(g) --> P4(s) + 6Cl2(g); dH*rxn = +1207 kJ
1681 kJ
If it takes 11.2 hours for 1.00 L of nitrogen (N2) to effuse through the pores in a balloon, how long would it take for 1.00 L of helium to effuse under the same conditions?
4.48 hours
Formic acid, HCHO2, can be decomposed to yield small quantities of carbon monoxide.
HCHO2(l) --> H2O(l) + CO(g)
If 3.85L of carbon monoxide was collected over water at 25*C and 689 mm Hg, how many grams of formic acid were consumed? PH2O@25*C = 23.76 mm Hg
6.34 g
You mix 45.0g of ice at -15.0*C with 165ml of water that was at 55*C. What is the final temp once the ice melts and mixes with the warm water?
specific heats: ice: 2.09 J/g-K
H2O: 4.18 J/g-K
steam: 1.84 J/g-K
for water: dHfus = 6.01 kJ/mole
dHvap = 40.67 kJ/mole
24.5*C
A neon sign is made of glass tubing whose inside diameter is 2.5 cm and whose length is 5.5 m. If the sign contains neon at a pressure of 1.78 torr at 35*C, how many grams of neon are in the sign? (The volume of a cylinder is 3.14r2h) 1 cm3 = 1 ml
0.005g of Ne
How much heat is released at constant pressure if 12.3 mL of 0.161 M silver nitrate is mixed with 41.7 mL of 0.493 M potassium chloride?
AgNO3(aq) + KCl(aq) -> AgCl(s) + KNO3(aq); dH* = -65.5 kJ
0.129 kJ
Use bond energy data to determine the enthalpy change for this reaction:
C2H6(g) + Cl2(g) --> C2H5Cl(g) + HCl(g)
In kJ/mole
C-C 348
C-H 413
C-Cl 328
H-Cl 431
Cl-Cl 242
-104 kJ
If 0.10 moles of I2 vapor can effuse from an opening in a heated vessel in 39 seconds, how long will it take 0.10 moles of H2 to effuse under the same conditions?
3.48 seconds
Magnesium nitride reacts with water according to the reaction below:
Mg3N2(s) + 6H2O(l) --> 3Mg(OH)2(s) + 2NH3(g)
What volume of ammonia gas at 20*C and 743 mm Hg will be produced from 4.56 g of magnesium nitride?
2.22L
Steam at 100*C was passed into a flask containing 275 g of water at 21*C, where the steam condensed, raising the temperature of this water to 83*C. How many grams of the steam must have condensed?
specific heats: ice: 2.09 J/g-K
H2O: 4.18 J/g-K
steam: 1.84 J/g-K
for water: dHfus = 6.01 kJ/mole
dHvap = 40.67 kJ/mole
31.11g of steam