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Chemical Kinetics

Nitric oxide reacts with hydrogen to give nitrogen and water:

2 NO + 2 H_{2} \to N_{2} + 2 H_{2} O

The kinetic of this reaction is explained by the following steps:

(i) 2NO + H₂ → N₂ + H₂O₂ (slow)
(ii) H₂O₂+ H₂ → 2H₂O (fast)
What is the predicted law?

2 NO + 2H₂ → N₂ + 2H₂O
The reaction involves 4 molecules but it has been found to be of third because it takes place in the following steps:

(i) 2NO + H₂ → N₂ + H₂O₂ (slow)

(ii) H₂O₂ + H₂ → 2H₂O (fast)

Step (i) being slow, is rate determining step.
The rate is given by

Rate = \frac{- dx}{dt} = \frac{d [N_{2}]}{dt} = k {[NO]}^{2} [H_{2}]

222 Views

For the reaction at 500 K
${NO}_{2} (g) + CO (g) \to {CO}_{2} (g) + NO (g)$
The proposed mechanism is as follow:
(i)
${NO}_{2} + {NO}_{2} \to NO + {NO}_{3} (slow) {NO}_{3} + CO \to {CO}_{2} + {NO}_{2} (fast)$
Predict the law?

Step I:
${NO}_{2} (g) + {NO}_{2} (g) \to_{slow}^{k} {NO}_{3} (g) + NO (g)$

Step II:
${NO}_{3} (g) + CO \to {NO}_{2} (g) + {CO}_{2} (g)$

$________________________________Overall reaction : {NO}_{2} (g) + CO (g) \to NO (g) + {CO}_{2} (g)__________________________________$

Step II is much faster than step I, that is k₂>> k₁ Step I is rate determining step and thus the rate of overall reaction equals to rate of step I. Step I is is a bimolecular process that has the rate law :

rate = k_{1} {[{NO}_{2}]}^{2} .

126 Views

Consider the reaction

A \overset{k}{\to} P .

The change in concentration of A with time is shown in the following plot:
(i) Predict the order of reaction.
(ii) Derive the expression for the time required for the completion of the reaction.

(i) Zero order reaction.
(i) Zero order reaction.(ii) Rate

(ii) Rate

rightwards double arrow negative fraction numerator straight d open square brackets straight A close square brackets over denominator dt end fraction space equals space straight k

rightwards double arrow space space space integral subscript open square brackets straight A close square brackets end subscript superscript open square brackets At close square brackets end superscript space minus space straight d open square brackets straight A close square brackets space equals space integral subscript 0 superscript straight t space straight k space dt

rightwards double arrow space space space space minus space open square brackets straight A close square brackets subscript open square brackets straight A close square brackets end subscript superscript open square brackets At close square brackets end superscript space equals space kt space plus space open square brackets straight C close square brackets rightwards double arrow space space space space space space space open square brackets straight A minus straight A subscript straight t close square brackets space equals space kt space plus space open square brackets straight C close square brackets rightwards double arrow space space space space space space space left square bracket straight A subscript straight t space minus space straight A right square bracket space equals space kt space plus space open square brackets straight C close square brackets rightwards double arrow space space space space space space space open square brackets straight A subscript straight t minus straight A close square brackets space equals space minus kt space minus space open square brackets straight C close square brackets rightwards double arrow space space space space space space space open square brackets straight A subscript straight t minus straight A close square brackets space equals space minus kt space plus space open square brackets straight A subscript 0 close square brackets rightwards double arrow space space space space space space space space space space open square brackets straight A close square brackets subscript straight t space equals space minus kt space plus space open square brackets straight A subscript 0 close square brackets

127 Views

Nitrogen dioxide reacts with fluorine to give

2 {NO}_{2} + F_{2} \to 2 {NO}_{2} F

The kinetic of this reaction is explained by the following steps.

(i) NO₂ + F₂→ 2NO₂F (slow)
(ii) NO₂ + F → NO₂F (fast)

What is the predicted law?

For the given reaction

2 {NO}_{2} + F_{2} \to 2 {NO}_{2} F

This reaction involves 3 molecules and proceeds in two steps:

(i) NO₂ + F₂ → 2NO₂F + F (slow)
(ii) NO₂ + F → NO₂F (fast)

The first stage being slow is the rate determining step. The rate is

Rate = \frac{d [{NO}_{2} F]}{dt} = k [{NO}_{2}] [F_{2}]

This indicates that the reaction is of second order.

187 Views

Express the rate of the following reaction in terms of disappearance of the reactants and appearance of products:
PCl₅(g) → PCl₃(g) + Cl₂(g)

PCl₅(g) → PCI ₃(g) + Cl₂(g)

rate =

\frac{d [{PCl}_{5}]}{dt} = \frac{d [{PCl}_{3}]}{dt} = \frac{d [{Cl}_{2}]}{dt}

232 Views

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Chemical Kinetics

For the reaction at 500 K
${NO}_{2} (g) + CO (g) \to {CO}_{2} (g) + NO (g)$
The proposed mechanism is as follow:
(i)
${NO}_{2} + {NO}_{2} \to NO + {NO}_{3} (slow) {NO}_{3} + CO \to {CO}_{2} + {NO}_{2} (fast)$
Predict the law?

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Chemical Kinetics

For the reaction at 500 K NO2(g) + CO(g) → CO2(g) + NO(g) The proposed mechanism is as follow:(i) NO2+NO2 → NO+NO3 (slow)NO3+CO → CO2+NO2 (fast) Predict the law?

For the reaction at 500 K
${NO}_{2} (g) + CO (g) \to {CO}_{2} (g) + NO (g)$
The proposed mechanism is as follow:
(i)
${NO}_{2} + {NO}_{2} \to NO + {NO}_{3} (slow) {NO}_{3} + CO \to {CO}_{2} + {NO}_{2} (fast)$
Predict the law?