(a) What is the rate of reaction? Write two factors that affect the rate of reaction?
(b) The rate of first order reaction increases from 4 × 10-2 to 8 × 10-2 when the temperature changes from 27° C to 37° C. Calculate the activation energy (Ea)
(Given: log2=0.301, log3 =0.4771, log4=0.6021)
OR
(a) for a reaction A + B → P, the rate is given by,
Rate = K [A][B]2
(i) How is the rate of reaction affected if the concentration of B is doubled?
(ii) What is the overall order of reaction if A is present in large excess?
(b) a first order reaction takes 23.1 minutes for 50% completion. Calculate the time required for 75% completion of this reaction. (log2=0.301, log3 =0.4771, log4=0.6021)
(a) the rate of reaction can be defined as the rate of appearance of concentration of product or rate of disappearance of concentration of reactant per unit time. The factors which can affect the rate of reaction are Temperature and presence / absence of catalyst. The reactant concentration, its physical state, surface site of reaction also affects the rate.
(b)Given:
K1 =4 × 10-2
K2= 8 × 10-2
T1= 27 + 273 = 300K
T2= 37 + 273 = 310 K
From Arrhenius equation
log
= 
Substituting the values we get
Log
= 
Log2=
Ea= 0.301 × 19.15× 9300
= 53606.50 Joules
= 53.61 KJ
OR
9(a) (i)
Rate = K [A][B]2
If the concentration of B is doubled
Rate = K [A][2B]2
Rate = K [A][4B]2
Rate = 4K [A][B]2
So, I can be seen that rate will increase by 4 times if the concentration of B is doubled.
(ii) for first order reaction
K= 
K= 0.693/23.1 = 0.03 /min
For first order reaction
k= 
log
For 75% completion
0.03= 
log
0.03= 
log4
T=
T=46.22 minutes.
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