CHEM_100/11                                                                                   2012

 

 

 

ASSIGNMENT #3                           Due to November 9

 

GAS LAWS and Chemical equilibrium

 

 

1. {4} The atmospheric pressure today in Antigonish is 740.0 mmHg.

(a)  {2} What is the pressure in kPa?

(b) {2} What is the pressure in atm?

 

2. {6} Calculate the pressure (in atm) of a sample of O2 gas (12.0g) in a steel vessel of 15.0 L at 18.0 oC.

 

 

 

3.  {5} A propellant in an aerosol spray has a pressure of 5.00 atm at 16o C.  Instruction on the can includes “do not expose to heat above 60o C or explosion may result”. What is the pressure inside the can at 61oC?

 

4.  {15} You synthesized a greenish-yellow gaseous compound of chlorine and oxygen and found that its density, d, is 7.71 g/L at 36oC and 2.88 atm.

(a) {10} Calculate the molar mass, M.

(b) {5} Using molar mass and atomic masses of Cl and O, determine the molecular formula by trial and error.

 

5. {10} It takes 68.3 s for a sample of N2 (g) to effuse through a tiny hole. Determine the molecular mass of gas whose effusion time under exactly the same conditions is 85.6s.

(remember that rate and time are inversely proportional)

                                                       

 

7. {10} Write the expressions for Kc for the following reactions. In each case indicate whether the rxn is homogeneous or heterogeneous.

(a) N2 (g)   +  O2 (g) à  2NO (g)

 (b) Mo (s)   + 2Cl2 (g)   à  MoCl4 (l)

(c) 2C2H4 (g)   + 2H2O (g) à 2 C2H6 (g)  + O2 (g)

(d) FeO (s)  + H2 (g) à Fe (s)  + H2O (l)

(e) 4HBr (aq)  +  O2 (g) à H2O (l)   + 2Br2 (l)

 

8 {10} Determine the value of Keq for the reaction of sodium and carbon dioxide in water using the data given below

2Na(s) + 2H2O(l) + 2CO2(g) D 2NaHCO3 (s) + H2 (g)

Na (s) + H2O (l) D NaOH (aq)  + ½ H2 (g)                      Keq = 7.3 x 1031

Na2CO3 (s) + H2O (l) D 2NaOH (aq) + CO2 (g)              Keq = 6.6 x 10-9

2NaHCO3 (s) D Na2CO3 (s) + H2O (l) + CO2 (g)            Keq = 1.1 x 10-5

 

 

 

9. {10} At 22 oC,  KP = 0.070 for the equilibrium

NH4HS (s)  à  NH3 (g)   +   H2S (g)

A sample of solid NH4HS is placed in a closed vessel and allowed to equilibrate.

 (a) {8}  Calculate the equilibrium partial pressure (atm) of ammonia, assuming that some solid NH4HS remains.

b) {2}  What is the total pressure in the vessel at equilibrium?

 

 

10.    {10} Consider the following reaction at equilibrium:

 2CO2 (g)   à  2CO (g)  + O2  (g)        ΔH = -514 kJ                 

How do the following changes affect the amount of CO(g) ?

 

(a)  increase temperature

(b) more CO2 added

(c) more O2 added

(a)    volume of the vessel is tripled

(b)   O2 is removed

(c)    Ar gas is added

(d)   total pressure is increased

(e)    a catalyst is added

(f)    remove  some CO2 (g)

(g)   decrease temperature

 

 

11 {5} For the equilibrium

  N2 (g) + 3 H2 (g) D 2NH3 (g)

the Kp = 4.51 x10-5  at 450 oC.

For the mixture below indicate the direction of this equilibrium reaction (toward product or toward reactants) at the following partial pressures:

105 atm NH3; 35 atm N2 ; 495 atm H2

 

  1. {15} at 1000C, Kc = 0.078 for the rxn:

SO2Cl2 (g) D SO2 (g) + Cl2 (g)

At the equilibrium, the concentrations of SO2Cl2  and SO2 are 0.108 M and 0.052 M, respectively. What is the partial pressure of Cl2 at equilibrium?