The decomposition of nitramide, O2NNH2, in water has the

following chemical equation and rate law. O2NNH2 (aq) yields N2O

(g) + H2O (l) rate= [O2NNH2]/[H] A proposed mechanism for this reaction is. k1 (1) O2NNH2 (aq) equilibrium O2NNH (aq) + H (aq) (fast

equilibrium) k-1 k2 (2) O2NNH (aq) yields N2O (g) + OH (aq) (slow) k3 (3) H (aq) + OH yields H2O (l) (fast) What is the relationship between the observed value of k and the

rate constants for the individual steps of the mechanism? k=__________ Also which symbols go into the numerator or demoniator k-1, k3,

k2, k1

General guidance

Concepts and reason

oThe rate constant of the reaction at a given temperature is defined as the rate of the reaction when the molar concentration of each of the reactants is unity.

oThe rate of the reaction depends on the reactant concentration.

oThe rate of a reaction is proportional to some power of the molar concentration of each of the reactants.

oThe rate constant can be determined by using the rate law.

Fundamentals

Rate of the reaction in terms of concentration of the reactants that determine the rate of the reaction is called the rate law or rate equation.

Rate law for a general reaction is

If the reaction proceeds through more than one step, then the overall rate of the reaction determined step is the slow step.

Step-by-step

Step 1 of 3

Consider the mechanism of the given reaction and write the rate law.

Step 1.

Step 2.

This is the overall rate determined step

Step 3.

Rate law of the decomposition reaction is

The reaction equation is given and the rate expression for each of the reactant species is also given. Consider this given reaction and write the rate law.

At the equilibrium, the rate of formation of is equal to the rate of decomposition of in step 2.

Do not get confused while writing the rate law for the reaction.

Example:

Correct

Wrong

Find the relation between the observed value of.

Step 2 of 3

Overall rate of the reaction is

Consider the rate of the step 1

Substitute the value of in equation (2)

Compare the equation (1) and (3) and find the relationship

Overall rate of the reaction is determined by the step 2 because it is the slow step among the other steps. Write the overall rate of the reaction, then compare the overall rate of the reaction and give rate of the reaction and find the relationship between the observed value of and the rate constants for the individual steps of the mechanism.

Take care while finding the equation for from the rate law

Example:

Correct

Incorrect

Find the numerator and denominator in the equation of found in step 2.

Step 3 of 3

Consider the equation of found in step 2.

Numerator is

Denominator is

The relationship between the observed value of and the rate constants for the individual steps of the mechanism is

Numerator is

Denominator is

The fraction contains two parts, top and bottom parts. The numerator is the top of the fraction and the denominator is the bottom of the fraction. So in fraction, are the numerators and is the denominator.

Take care while find the denominator and numerator of the fraction.

Example:

Correct;

Numerator is

Denominator is

Incorrect

Numerator is

Denominator is

Answer

The relationship between the observed value of and the rate constants for the individual steps of the mechanism is

Numerator is

Denominator is

Answer only

The relationship between the observed value of and the rate constants for the individual steps of the mechanism is

Numerator is

Denominator is

cC+dD—>product

rate=k[A] [B]’, Where k is called the rate constant

0,NNH, (aq)0,NNH(aq)+H(aq) rate=k, [0,NNH,] rate=k, [0,NNH][H] Here, k, [0,NNH,]=k, [0,NNH][H]

O,NNH(aq) k>N,0(g)+OH(aq) rate=k, [O,NNH]

H(aq) +OHks »H,0(1) rate=kz [H](OH)

rate=k[, NNH, H

O,NNH

O,NNH,

O,NNH(aq) k>N,0(g)+OH(aq) rate=k, [O,NNH]

O,NNH(aq) k>N,0(g)+OH(aq) rate=ką [N,0][04]

k, k, k.,,andk

rate=k, [0,NNH)….(2)

k[O,NNH,]=k., [0,NNH][H] TO Nnul_k, [0,NNH,] (0,NNH] =– , [H]

O,NNH

rate=k,x [2NNH, I k,[H] rate = k;*k, x [0,NNH,] k [H]

rate=k O2NNH, 1 ……… (1) k,xk, [0,NNH,] rate=-*. *[H] (3)

O,NNH

k[O,NNH,]=k., [0,NNH][H] TO Nnul_k, [0,NNH,] (0,NNH] =– , [H]

k [O,NNH,]=k.,[ONNH][H] k,[H] (O,NNH]=k, (O,NNH,]

k=k,xk

k, andk

k2xk,

k, andk

k=k,xk

k, andk

k=k,xk

k, andk

k=k,xk

k, andk

k=k,xk

k, andk

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