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Chemical Kinetics

Short Answer Type

131. Identify, giving reasons, the faster reaction in the following:

2 Na (s) + I_{2} (s) \to 2 Nal (s)

2 Na (s) + I_{2} (g) \to 2 Nal (s)

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132. Identify, giving reasons, the faster reaction in the following:

C (s) + 2 H_{2} O (g) \to 2 H_{2} (g) + {CO}_{2} (g)

C (s) + 2 H_{2} O (s) \overset{Catalyst}{\to} 2 H_{2} (g) + {CO}_{2} (g)

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133. Identify, giving reasons, the faster reaction in
the following:

C (s) + 1 / 2 O_{2} (g) \overset{500 °}{\to} CO (g) C (s) + 1 / 2 O_{2} (g) \overset{1000 °}{\to} CO (g)

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134. Identify, giving reasons, the faster reaction in the following:

N_{2} (10 atm) + 3 H_{2} (10 atm) \to 2 {NH}_{3} (g) N_{2} (5 atm) + 3 H_{2} (5 atm) \to 2 {NH}_{3} (g)

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135. What is the difference between order and molecularity of a reaction?

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Long Answer Type

136. What are Pseudo chemical reaction? Give examples.

These are the reactions which follow kinetics of lower order whereas by appearance these appear to be reactions of higher order. In other words, these are false or pseudo in nature. In these reactions one of the reactants (genrally water) is reprsent in such a large excess that its concentration remain practially unchanged during the reaction. Therefore, the concentration of such a reactant does not appear in the rate law for the reaction.
Examples: (i)

C_{12} H_{22} O_{11} + H_{2} O \overset{H^{+}}{\to} C_{6} H_{12} O_{6} + C_{6} H_{12} O_{6} Glucose Fructose reaction rate (r) = k [Sucrose] [H_{2} O] [H_{3} O]^{+} = k^{1} (Sucrose)

(ii)

{CH}_{3} {COOC}_{2} H_{5} + H_{2} O \overset{H^{+}}{\to} Ethylacetate {CH}_{3} COOH + C_{2} H_{5} OH Acetic Ethyl acid alcohol

reaction rate (r) = k [{CH}_{3} {COOC}_{2} H_{5}] [H_{2} O] {H_{3} O^{+}] = k^{1} ({CH}_{3} {COOC}_{2} H_{5})

558 Views

Short Answer Type

137. A reaction is first order in A and second order in B.
(i) Write differential rate equation.
(ii) How is the rate affected if the concentration of B is tripled?
(iii) How is the rate affected when the concentrations of both A and B are doubled?
What is the significance of rate constant in the rate expression?

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138. Following reaction takes place in one step:

2 NO (g) + O_{2} (g) ⇋ 2 {NO}_{2} (g)

How will the rate of the above reaction change if the volume of the reaction vessel is diminished to one third of its original volume? Will there be any change in the order of the reaction with the reduced volume ?

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139. Two similar reactions have the same rate constant at 25°C, but at 35°C one of the reaction has a higher rate constant than the other. Account for these observations.

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Long Answer Type

140. How will you verify whether a reaction is first order or not?

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