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Chemical Kinetics

Short Answer Type

91. Write the rate of reaction for the following reactions in terms of the concentration of reactants and products
(i) 2H₂O₂→ 2H₂O + O₂(ii) 2NO + O₂ → 2NO₂

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92.

Nitric Oxide. NO reacts with oxygen to produce nitrogen dioxide.
2NO(g) + O₂(g) → 2NO₂(g)
The rate law for this reaction is
rate = k[NO]² [O₂]
Propose a mechanism for the above reaction.

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93. State the role of activated complex in a reaction and state its relation with activation energy?

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94. For the reaction:
2NO(g)+ O₂(g) → 2NO₂(g)
the rate law is
Rate = k[NO]². Why does the rate law not include the concentration of O₂?

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95.

The rate of reaction
2NO + Cl₂ → 2NOCl
is double when concentration of Cl₂ is doubled and it becomes 8 times when concentrations of both NO and Cl₂ are doubled. Deduce the order of this reaction.

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96. Define ‘energy of activation’ of a reaction. How does it vary with a rise in temperature?

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Long Answer Type

97. State and explain Arrehenius equation. How can we determine the activation energy of a reaction using this equation?

k = {Ae}^{- E_{a} / RT} .

where k is rate constant, A is Arrhenius of frequency factor, E_a is energy of activation, T is absolute temperature. This equation is called Arrhenius equation.

Taking log, we get

In k = In A - \frac{E_{a}}{RT}

2.303 \log k = 2.303 \log A - \frac{E_{a}}{RT} \log k = \log A - \frac{E_{a}}{2.303 RT}

Plot of log k versus 1 / T is a straight line with a negative slope. The slope of the line is equal to

Slope = - \frac{E_{a}}{2.303 R}

∴

E_{a} = - slope \times 2.303 \times R

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98. What are Photo-chemical reactions? Describe the mechanism of reaction between hydrogen gas and chlorine gas when exposed to sunlight?

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Short Answer Type

99. From the potential energy diagram show that: ΔE = over all energy change for the forward reaction: Ea₁ – Ea₂; where Ea₁ = Activation energy for the forward process and Ea₂ = Activation energy for the reverse process?

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100. The form of the rate law for a reaction is expressed as: rate = k [Cl₂] [NO]². Find out the orders of reaction with respect to Cl₂ and with respect to NO and also the overall order of the reaction.

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