Moh ler skor kimi-'A'!

  Moh Ler Skor A kimi-‘A’!

UPS II PDT KMS

Name        : __________________________

Matrix no : __________________________

Tutor       : DM  P

CHAPTER 5 : STATES OF MATTER

1.         A vessel of fixed volume 2.0 dm³ contains 0.2 mol of calcium carbonate.  After heating, it was found

            that the pressure of the gas formed at 30 ºC is 44.08 kPa.

            (a)  Write an equation for the decomposition of calcium carbonate.

            (b)  Calculate the number of moles of gas formed from the decomposition of  calcium carbonate.

            (c)  Determine the mass of calcium carbonate left in the vessel.

2.         1.490 g of zinc reacted with excess hydrochloric acid and the hydrogen gas evolved  was collected using the water displacement method at a temperature of   30 ºC and a pressure of 100.6 kNm² .  The vapour pressure of water at this temperature is 5.81 kNm^-2.  Calculate the volume of dry hydrogen gas collected.

            [Ar of Zn = 65, H = 1, Cl = 35.5 ]

3.         (a) Explain why real gases do not obey the ideal gas equation.

      (b) Under what conditions does the behaviour of real gases approach ideality?

            Explain your answer.

4.         (a) Define the boiling point of a liquid.

            (b) Discuss the factors that affect the boiling point of pure liquids.

CHAPTER 6: CHEMICAL EQUILIBRIUM

1. (a)  The K_c value at 300^oC for the reaction

                  A(g)       +     2B(g)  <----->  AB₂(g)

           is  0.90. A mixture of these gases was analysed and found to contain 0.04 M of A, 0.50 M of B and 

           0.04 M of AB₂ Has the system reached equilibrium ?  In which direction must the reaction proceed to 

           achieve equilibrium ?

     (b)  A system was charged with 0.400M of ammonia gase, NH₃ and was allowed to attain equilibrium at

            472^oC. The equilibrium mixture of gases was analysed at the same temperature and the

           concentration of N₂ found was 0.025 M. Calculate the

i.                    K_c

ii.                  K_p

iii.                Percent dissociation of NH₃

2. Ammonia hydrogen sulfide decomposes according to the following reaction:

NH₄HS(s) <----->   H₂S(g)  +  NH₃(g)

    The equilibrium constant, Kp for the reaction is 0.11 atm² at 250^oC. If 10.0 g of NH₄HS(s) is placed in a

     sealed 4.0 dm³ container at 250^oC, determine

a)      The partial pressure of each gas at equilibrium.

b)      The degree of dissociation of NH₄HS.

3. Consider the following equilibrium:

4NH₃(g)  +  3O₂(g) <-----> 2N₂(g)  +  6H₂O(g)                ΔH = -1531 kJ

     Predict the effect on the equilibrium position when the following changes are made to system. Explain.

a)      Some of the ammonia is removed from the system.

b)      The pressure of the system is increased.

c)      The temperature of the system is raised.

d)     Helium is added at a constant volume.

e)      Helium is added at a constant pressure.

f)       A catalyst is added to the reaction mixture. .

4. At 448 ^oC, the K_c for the reaction H₂(g) + I₂(g) <-----> 2HI(g) is 51. Predict how the reaction will 

    proceed to reach equilibrium if starting with 1.0 x 10^-2 M HI, 5.0 x 10^-3 M H₂ and 1.5 x 10^-2 M I₂.

5. Consider the following exothermic gas phase reaction at equilibrium

           4HCl (g)   +   O2 (g) <----> 2Cl2 (g)   +   2H2O (g) 

  If the concentration of HCl(g) were suddenly increased, describe what would happen to:

a)      the concentration of O₂(g)

b)      the concentration of Cl₂(g)

c)      the concentration of H₂O(g)

d)     the value of the equilibrium constant, K_c

   Good Luck in your UPS II Chem Thursday 2.2.12 9-10 am