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## Order of reaction-

### Solution )

(i) Rate = dx / dt = K [A] 1/2 [B]3/2

order of reaction = 1/2 + 3/2 =2

#### Reaction is second order.

(ii) If reaction is zero order then,

### (i) 2 H2 + 2 NO ——–> 2 H2O + N2

Rate = K [H2][NO]2

### (ii) H2O2 + 3 I– + 2 H+ ——–> 2 H2O + I3– (aq.)

Rate = K [H2O2][I]

### (iii) CH3CHO ———> CH4 + CO

Rate = K [CH3CHO]3/2

### Solution)

(i) Rate = K [H2][NO]2

Order of reaction = 1 + 2 = 3

### Unit of  K –

Rate = K [H2][NO]2

K = Rate /  [H2][NO]2

unit of K = (mole litre-1 sec-1) / (mole litre-1 )(mole litre-1 )2

#### Unit of K = litre2 mole -2sec-1 Ans.

(ii)

Rate = K [H2O2][I]

Order of reaction = 1 + 1 = 2

### Unit of  K-

Rate = K [H2O2][I]

K = Rate /  [H2O2][I]

unit of K = (mole litre-1 sec-1) / (mole litre-1 )(mole litre-1 )

#### Unit of K = litre mole-1 sec-1 Ans.

(iii)

Rate = K [CH3CHO] 3/2

### Unit of  K-

Rate = K [CH3CHO]3/2
K = Rate / [CH3CHO]3/2

unit of K = (mole litre-1 sec-1) / (mole litre-1 )3/2

#### Unit of K = litre1/2 mole -1/2 sec-1 Ans.

Q 3) -The rate of reaction,

2A + B ——–> A2B has the rate law,

Rate = K[A]2 with rate constant equal to 0.50 mole -1 litre sec-1. Calculate the rate of reaction when,

(i) [A] = 0.60 mole / litre , [B] = 0.05 mole/litre

(ii) When conc. of A and B have been reduced to 1/4.

Solution)

(i)  K = 0.50 mole -1 litre sec-1 , [A] = 0.60 mole /litre

Rate of reaction = K[A]= 0.50 x 0.60 x 0.60

#### Rate of reaction = 0.18 Ans.

(ii)

K = 0.50 mole -1 litre sec-1 , [A] = 0.60 x 1/4  mole /litre

Rate of reaction = K[A]2

= 0.50 x 0.60 x 0.60/ 4 x 4

#### Rate of reaction = 0.011  Ans.

Q 4) The reaction  ,  2NO + O2 ——> 2 NO2 follows the rate law,

Rate = K [NO]2[O2]. If K = 2 x 10 -6 litre2 mole-2sec -1. Calculate rate of reaction when [NO] = 0.04 mole /litre and

[O2] = 0.2 mole / litre.

Solution )

[NO] = 0.04 mole /litre ,  [O2] = 0.2 mole / litre , K = 2 x 10 -6 litre2 mole-2sec -1.

Rate = K [NO]2[O2] = 2 x 10 -6  [0.04]2 [0.2]

Rate =6.4 x 10 -10 mole litre-1 sec-1 Ans.