Hydrogen iodide gas decomposes to form an equilibrium mixture of hydrogen gas and
iodine gas at 4400C. At this temperature, equilibrium constant, Kc,for the reaction is 0.02.
a) i)Write equation for the reaction and expression for the equilibrium constant, Kc.
(2½ marks)
ii) 2 moles of hydrogen and 1 mole of iodine were mixed together in a 1.0dm3vessel at
4400C. Calculate the number of moles of iodinethat reacted. (3 marks)
iii) Describe how equilibrium constant, Kc, for formation of hydrogen iodidegas from
iodine and hydrogen can be determined by a titrimetric method. (5 marks)
b) What is the significance of each of the following in rates of reactions?
i) Rateconstant (2 marks)
ii) Activatedstate (2 marks)
c) Rate constant (k) for the decomposition of hydrogen iodide at different temperatures is
given in the table below.
Rate constant, k (mol-1dm3 s
-1
)Temperature(K)
3.75 x 10-9500
6.65 x 10-6600
1.15 x 10-3700
7.75 x 10-2800
i) Plot a graph of lnkagainst

. (3 marks)
ii) Use your graph to obtain the value of activation energy (Ea) for thedecomposition of
hydrogen iodide.(The gas constant, R = 8.3Jmol1K1
) (2½ marks)