Problems for Chpt. 4,5,6
Chpt. 4
1. For each of the following reactions, write a balanced molecular, ionic and net ionic equation.
You must include state symbols. If no reaction occurs write no reaction.
(a)
The reaction of a solution of nitric acid with a solution of barium hydroxide.
(b)
The reaction of a solution of barium chloride with a solution of sodium sulfate.
(c)
The reaction of a solution of sodium acetate with a solution of hydrochloric acid.
(d)
The reaction of a solution of ammonia with a solution of hydrochloric acid.
(e)
The reaction of a solution of hydrobromic acid with a solution of sodium
hydrogen carbonate.
(f)
The reaction of a solution of hydrochloric acid with zinc metal.
(h)
The reaction of a solution of acetic acid with a solution of potassium hydroxide.
2. Calculate the mass of precipitate formed when 110.0 mL of a 0.100 M Ba(NO3)2 solution is
added to 140.0 mL of a 0.100 M Na2SO4 solution. Calculate the concentrations of all ions in the
remaining solution.
3. A sodium hydroxide solution of unknown concentration is used to titrate a solution
containing 865 mg of KHP (KHC8H4O4 , molar mass = 204.22 g/mol ). Unfortunately an excess
of the sodium hydroxide solution is added to the KHP solution. The excess sodium hydroxide is
titrated with 1.47 mL of a 0.1134 M HCl solution. Assuming that 37.33 mL of the sodium
hydroxide solution was added to the KHP solution, calculate the concentration of the sodium
hydroxide solution.
4. For each of the following indicate whether or not the reaction is a redox reaction. If the
reaction is a redox reaction indicate which species is oxidized, which is reduced, and how many
moles of electrons are transfered for each mol of reaction.
(a) Cu (s) + 2 Ag(NO3) (aq) → 2 Ag (s) + Cu(NO3)2 (aq)
(b) HCl (g) + NH3 (g) → NH4Cl (s)
(c) 16 H+ (aq) + 2 Cr2O72- (aq) + C2H6O (l) → 4 Cr3+ (aq) + 11 H2O (l) + 2
CO2 (g)
(d) 4 HNO3 (aq) + H2O (l) + 3 As2O3 (s) →
4 NO (g) + 6 H3AsO4 (aq)
Chpt. 5
5. A 4.85 L sample of HCl gas at S.T.P is completely dissolved in enough water to yield 425
mL of an aqueous HCl solution. To this solution is added exactly 500 mL of a 4.10 x 10-1M
NaOH solution.
(a)
Is the resulting solution acidic or basic?
(b) Calculate the concentrations of all ions in the resulting solution.
6. A gas cylinder contains 3.78 kg of nitrogen gas at a temperature of 250C and a pressure of
8.0 MPa. Some of the gas is removed and the pressure drops to 6.3 MPa. Calculate the mass of
nitrogen gas that remains assuming that the temperature remains constant at 250C.
7. Suppose that nitrosyl chloride gas (NOCl) is produced by reacting 6.00 g of chlorine gas
with 5.00 g of nitric oxide gas (NO).
(a) If the reaction is carried out in a 15.0 L container at a constant temperature of 35.00C,
calculate the total pressure in the container after the reaction is completed.
(b) If the reaction is carried out at a constant pressure of 1.00 atm and a constant temperature of
35.00C, calculate the volume of the container and the partial pressure of nitrosyl chloride gas
after the reaction is complete.
8. A piece of zinc metal is reacted with an excess of aqueous hydrochloric acid. The hydrogen
gas which is produced is collected by displacement over water. If the total pressure of the gas
collected is 758 torr, the volume of the gas is 250 mL, and the temperature of the gas is 24.00C,
calculate the mass of zinc reacted. (The vapor pressure of water at 240C is 22.4 torr)
9. The density of an ideal gas at 300C and 740 torr is 2.78 g/L . Determine the molar mass of
this gas.
10. Consider the following reaction.
4 NH3 (g) + 5 O2 (g)
→
4 NO (g) + 6 H2O (g)
Suppose we have two flasks connected by a stopcock (see figure 13.20 on page 445). In
one flask we have 2.00 L of NH3 (g) at a pressure of 0.500 atm. In the other flask we have
1.00 L of O2 (g) at a pressure of 1.50 atm. When the stopcock is opened the gases mix,
and react according to the equation above.
(a) Calculate the partial pressure of all gases after the reaction is complete.
(b) Calculate the total pressure after the reaction is complete.
You may assume that the total volume of the apparatus is 3.00 L.
11. A 3.417 g sample of manganese metal is reacted with excess HCl (aq) to produce 3.22 L of
H2 (g) at 300 K and 0.951 atm. and a manganese chloride compound. What is the formula of the
manganese chloride compound produced in the reaction?
12.
Consider 1 mol of each of the following gases at STP.
H2, Xe, Cl2, O2
(a) Rank the gases in order of increasing kinetic energy.
(b)
Rank the gases in order of increasing average speed.
(c) Rank the gases in order of increasing volume.
(d) Rank the gases in order of increasing density.
13.
It rate of effusion of a particular gas was measured and found to be 24.0 mL/min. Under
identical conditions the rate of effusion of methane gas was measured and found to be 47.8
mL/min. What is the molar mass of the unknown gas?
14. Suppose it takes 4.5 minutes for 1.0 L of He gas to effuse through a pinhole. How long
will it take for 1.0 L of Cl2 gas to effuse under identical conditions?
Chpt. 6
15.
The molar heat capacity (expressed in units of J/mol k) of a substance under conditions
of constant volume is defined as,
Cv = qv/nT .
The molar heat capacity (expressed in units of J/mol k) of a substance under conditions of
constant pressure is defined as,
Cp = qp/nT .
(a) Show that the molar heat capacity of an ideal monatomic gas under conditions of constant
volume is,
Cv = (3/2)R
.
(Remember that for an ideal monatomic gas , E =n(3/2)RT )
(b) Show that the molar heat capacity of an ideal monatomic gas under conditions of constant
pressure is,
Cp = (5/2)R
.
16. Suppose that 5.00 g of He (g) is pumped into a balloon at a temperature of 298 K and a
pressure of 1.00 atm. Next, 3.50 x 103 J of heat is added to the balloon while the pressure
remains constant.
(a) Calculate the final temperature and volume of the He (g) inside the balloon assuming that
the balloon expands against a constant external pressure of 1.00 atm.
(b) Calculate the change in internal energy ( E) for the He (g).
17. In a coffee-cup calorimeter, 1.60 g of NH4NO3 is mixed with 75.0 g of water at an initial
temperature of 25.00OC.
After the salt dissolves the final temperature of the solution is 23.34 OC. Assuming that the
solution has a heat
capacity of 4.18 J/g OC, calculate H for the dissolving of NH4NO3 (the
enthalpy of solution) in kJ/mol.
18. When 1.00 L of 2.00 M Na2SO4 solution at 30.0 OC is is mixed with 2.00 L of 0.750 M
Ba(NO3)2 solution at
30.0 OC in a coffee-cup calorimeter a precipitate of BaSO4 forms. The temperature of the
mixture rises to 42.0 OC. Assuming that the specific heat capacity of the resulting solution
is 6.37 J/g OC and that the density of the resulting solution is 2.00 g/mL, calculate H for
the precipitation reaction in kJ/mol.
19. In order to calibrate a bomb calorimeter , 3000 g of water is added to the calorimeter. next,
1.08 x 10-2 mol of ethanol (C2H6O) is combusted in the presence of excess oxygen according to
the equation,
C2H6O (l) + 3 O2 (g)
>
3 H2O (l) + 2 CO2 (g)
E = - 1365 kJ/mol .
Assuming that the temperature of the water increases by 0.966 oC calculate the heat capacity of
the empty calorimeter (the calorimeter without water). (Remember that the specific heat of
water is 4.18 J/g K)
20. Suppose that 1.048 g of benzene is combusted in a bomb calorimeter which contains 945 g
of water. The temperature of the water increases from 23.640 OC to 32.681 oC. The heat
capacity of the empty calorimeter is 891 J/ OC .
C6H6 (l) + 15/2 O2 (g)
>
3 H2O (l) + 6 CO2 (g)
(a) Calculate E for the combustion of benzene in kJ/mol .
(b) Calculate H for the combustion of benzene in kJ/mol. Assume that the volumes of all
liquids are negligible compared to the volumes of the gases and that the temperature is 298 K.
21. Suppose that 50.0 mL of a 0.250 M HCl solution is mixed with 50.0 mL of a 0.100 M
Ba(OH)2 solution in a coffee-cup calorimeter. The temperature of the resulting solution
increases by 1.76 oC . Calculate H for the reaction between HCl (aq) and Ba(OH)2 (aq) in kJ
per mole of Ba(OH)2 reacted. Assume that the specific heat capacity of the resulting solution is
4.18 J/g oC and that the density of the resulting solution is 1.00 g/mL . Also assume that the heat
capacity of the calorimeter itself can be ignored.
22.
Consider the following data
2 O3 (g) → 3 O2 (g)
H = -427 kJ
O2 (g) → 2 O (g)
H = + 495 kJ
NO (g) +
O3 (g) → NO2 (g) + O2 (g)
(a) Calculate H for the following reaction.
NO (g) + O (g) → NO2 (g)
(b) Calculate  for the following reaction assuming T =350 K
NO (g) + O (g) → NO2 (g)
H = -199 kJ
23.
Consider the following reaction
AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3
(aq)
H = -66 kJ
Suppose that 100.0 mL of 0.100M AgNO3 is added to 200.0 mL of 0.100 M NaCl in a
coffee cup calorimeter. Assuming that the initial temperature of the solution is 25.000C
calculate the final temperature of the solution. You may assume that the specific heat
capacity of the solution is 4.18 J/g 0C and that the density of the solution is 1.00 g/mL.
Also assume that the heat capacity of the cup itself and the precipitate is negligible.