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 Kc value at 300oC 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
472oC. The equilibrium mixture of gases was analysed at the same temperature and the
concentration of N2 found was 0.025 M. Calculate the
i. Kc
ii. Kp
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 250oC. If 10.0 g of NH4HS(s) is placed in a
sealed 4.0 dm3 container at 250oC, 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 Kc 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, Kc
Good Luck in your UPS II Chem Thursday 2.2.12 9-10 am