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Question : 12
Total: 12
Read the following passage and answer the question that follow:
The rate of reaction is concerned with decrease in concentration of reactants or increase in the concentration of products per unit time. It can be expressed as instantaneous rate at a particular instant of time and average rate over a large interval of time. A number of factors such as temperature,
concentration of reactants, catalyst affect the rate of reaction. Mathematical representation of rate of a reaction is given by rate law:
Rate = k [ A ] x [ B ] y
x y x + y
When a sequence of elementary reaction gives us the products, the reaction is called complex reaction. Molecularity and order of an elementary reaction are same. Zero order reaction are relatively uncommon but they occur under special condition. All natural and artificial radioactive decay of unstable nuclei take place by first order kinetics.
(a) What is the effect of temperature on the rate constant of a reasons.
(b) For a reactionA + B → k [ A ] 2 [ B ] 1 ∕ 2
(c) How order and molecularity are different for complex reactions?
(d) A first order reaction has a rate constant2 × 10 − 3 s − 1 6 g 2 g
OR
The half life for radioactive decay of14 C 75 % 14 C
[ log 4 = 0.6021 , log 3 = 0.4771 , log 2 = 0.3010 , log 10 = 1 ]
The rate of reaction is concerned with decrease in concentration of reactants or increase in the concentration of products per unit time. It can be expressed as instantaneous rate at a particular instant of time and average rate over a large interval of time. A number of factors such as temperature,
concentration of reactants, catalyst affect the rate of reaction. Mathematical representation of rate of a reaction is given by rate law:
When a sequence of elementary reaction gives us the products, the reaction is called complex reaction. Molecularity and order of an elementary reaction are same. Zero order reaction are relatively uncommon but they occur under special condition. All natural and artificial radioactive decay of unstable nuclei take place by first order kinetics.
(a) What is the effect of temperature on the rate constant of a reasons.
(b) For a reaction
(c) How order and molecularity are different for complex reactions?
(d) A first order reaction has a rate constant
OR
The half life for radioactive decay of
Solution:
(a) The rate constant ( k 10 ∘
k =
(b) According to the equation,r = k [ A ] 2 [ B ] 1 ∕ 2
Order of the reaction= 2 +
=
(c) Order of reaction is defined as the sum of the powers of the molar concentration of the reaction species in the rate equation of the reaction. It is applicable for both elementary and complex reactions.
Molecularity of a reaction is defined as the total number of reacting species participating in an elementary reaction. It has no significance for complex reactions as applicable for only elementary reactions.
(d)k = 2 × 10 − 3 s − 1
t =
log
t =
log
t = 1151.5 × 0.4771 = 549.3 s
OR
According to first order reaction,
Half-life ( t 1 ∕ 2 ) =
t 1 ∕ 2 = 6980 years
k = 0.693 ∕ 6980
However, the time taken can be calculated using first order rate of reaction when wood contain only75 % C 14
Initial concentration ofC 14 , [ R ] 0 = 100
Amount at timet s , [ R ] = 75
t =
log
t =
log
t = 2898 years
Thus, the age of the sample is approximately 2898 years.
(b) According to the equation,
Order of the reaction
(c) Order of reaction is defined as the sum of the powers of the molar concentration of the reaction species in the rate equation of the reaction. It is applicable for both elementary and complex reactions.
Molecularity of a reaction is defined as the total number of reacting species participating in an elementary reaction. It has no significance for complex reactions as applicable for only elementary reactions.
(d)
OR
According to first order reaction,
However, the time taken can be calculated using first order rate of reaction when wood contain only
Initial concentration of
Amount at time
Thus, the age of the sample is approximately 2898 years.
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