PTT 107 Physical Chemistry (Assignment: Chemical Kinetics)
Sem II 2011/2012
Submission date: 25th May 2012
Question 1
The rate of the reaction A + 2B  3C + D was reported as 2.7 mol dm-3 s-1. State the rates of
formation and consumption of the participants.
Question 2
The rate of formation of C in the reaction 2A + B  2C + 3D is 2.7 mol dm-3 s-1. State the reaction
rate, and the rates of formation or consumption A, B, and D.
Question 3
The rate constant for the first-order decomposition of N2O5 in the reaction 2N2O5(g)  4NO2(g) + O2(g)
is kr = 3.38 x 10-5 s-1 at 25oC.
a) What is the half life of N2O5
b) What will be the pressure, initially 500 Torr at
i) 50 s
ii) 20 mins
Question 4
Using the a) rate-determining step approximation,
b) Steady-state approximation
Devise the rate law for the decomposition of N2O5,
2𝑁2 𝑂5(𝑔) → 4𝑁𝑂2(𝑔) + 𝑂2(𝑔)
On the basis of the following mechanism:
𝑁2 𝑂5 → 𝑁𝑂2 + 𝑁𝑂3
𝑁𝑂2 + 𝑁𝑂3 → 𝑁2 𝑂5
𝑁𝑂2 + 𝑁𝑂3 → 𝑁𝑂2 + 𝑂2 + 𝑁𝑂
𝑁𝑂 + 𝑁2 𝑂5 → 𝑁𝑂2 + 𝑁𝑂2 + 𝑁𝑂2
𝑘𝑎
𝑘−𝑎
𝑘𝑏
𝑘𝑐
Question 5
The reaction 𝐶𝑂2(𝑎𝑞) + 𝐻2 𝑂 → 𝐻 + + 𝐻𝐶𝑂3− catalyzed by the enzyme bovine carbonic anhydrase
was studied in a stopped-flow apparatus at pH 7.1 and temperature 0.5oC. For an initial enzyme
concentration of 2.8 x 10-9 mol dm-3, initial rates as a function of [CO]0 are (where 𝑐 𝑜 ≡ 1 𝑚𝑜𝑙/
𝑑𝑚3 ):
103[CO2]0/co
104r0/(c0 s-1)
1.25
0.28
2.50
0.48
Find k2 and KM from a Lineweaver-Burk plot.
5.00
0.80
20.0
1.5