Zinc or silver-oxide cell is used in hearing aids and electric watches. The following reactions occur: Zn ( s ) → Zn 2 + ( ag ) + 2 e - , E ° Zn 2 + / Zn = 0 . 76 V Ag 2 O + H 2 O + 2 e - → 2 Ag + 2 OH - , E ° Ag + / Ag = 0 . 34 V Calculate, (a) the standard potential of the cell. (b) standard Gibbs free energy.

Given : E ° ( cathode ) = 0 . 34 V E ° ( anode ) = - 0 . 76 V Solution : a. E ° cell = E ° cathode - E ° anode = 0 . 34 - ( - 0 . 76 ) = 1 . 104 V b. Gibbs' Energy of the reaction is given by ∆ G = - nFE ° cell = - 2 × 96500 C mol - 1 × 1 . 104 V = - 2 . 13 × 10 5 J mol - 1

For the reaction, N 2 + 3 H 2 → 2 NH 3 , the rate of change of concentration for hydrogen is 0 . 3 × 10 - 4 Ms - 1 . What will be the rate of change of concentration of ammonia?

Given: ∆ [ H 2 ] ∆ t = 0 . 3 × 10 - 4 M s - 1 . Solution: For the given reaction, N 2 + 3 H 2 → 2 NH 3 , Rate of reaction ( r ) = - ∆ [ N 2 ] ∆ t = - 1 3 ∆ [ H 2 ] ∆ t = + 1 2 ∆ [ NH 3 ] ∆ t . The rate of change in concentration of NH 3 : ( r ) = - 1 3 ∆ [ H 2 ] ∆ t = + 1 2 ∆ NH 3 ∆ t ∆ NH 3 ∆ t = 2 3 × ∆ [ N 2 ] ∆ t = 2 3 × 0 . 3 × 10 - 4 = 0 . 2 × 10 - 4 M s - 1

For a reaction between A and B, the initial rate of reaction is measured for various initial concentrations of A and B . The data provided is : A B Initial rate mol L - 1 s - 1 0 . 020 0 . 010 2 . 40 × 10 - 4 0 . 020 0 . 030 2 . 16 × 10 - 3 0 . 040 0 . 030 4 . 32 × 10 - 3 Calculate the overall order of the reaction.

Rate law can be given as : Rate, r = k A x B y , where k is rate constant. For the given reactant concentrations, rate equations can be given as : 2 . 40 × 10 - 4 = k 0 . 020 x 0 . 010 y 2 . 16 × 10 - 3 = k 0 . 020 x 0 . 030 y 4 . 32 × 10 - 3 = k 0 . 040 x 0 . 030 y Dividing the first two rate equations : 2 . 40 × 10 - 4 2 . 16 × 10 - 3 = k 0 . 020 x 0 . 010 y k 0 . 020 x 0 . 030 y 3 y = 9 y = 2 Dividing the second and third rate equations : 4 . 32 × 10 - 4 2 . 16 × 10 - 3 = k 0 . 040 x 0 . 030 y k 0 . 020 x 0 . 030 y 2 x = 2 x = 1 The over order of reaction = 2 + 1 = 3 .

E M B I B E

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 13

MEDIUM

12th ICSE

IMPORTANT

Earn 100

State the principles which serve as basis for the refining by liquation in metallurgy.

Important Questions on Sample Question Paper 4

EASY

12th ICSE

IMPORTANT

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 14

Explain the following observations: (i) Electrophilic substitution in the case of aromatic amines takes place more readily than benzene.

EASY

12th ICSE

IMPORTANT

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 14

Explain the following observations:

Tertiary amines do not undergo acylation.

EASY

12th ICSE

IMPORTANT

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 15

Calculate the charge in coulombs required for the oxidation of

2

moles of water to oxygen. [Given,

1 F = 96500 C {mol}^{- 1}

]

HARD

12th ICSE

IMPORTANT

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 15

Zinc or silver-oxide cell is used in hearing aids and electric watches. The following reactions occur:

Zn (s) \to {Zn}^{2 +} (ag) + 2 e^{-}, E^{°} {Zn}^{2 +} / Zn = 0.76 V {Ag}_{2} O + H_{2} O + 2 e^{-} \to 2 Ag + 2 {OH}^{-}, E^{°} {Ag}^{+} / Ag = 0.34 V

Calculate, (a) the standard potential of the cell. (b) standard Gibbs free energy.

HARD

12th ICSE

IMPORTANT

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 16

Consider the reaction, $A \to P$ . The change in the concentration of A with time is shown in the following plot.

Question Image

Predict the order of reaction.

HARD

12th ICSE

IMPORTANT

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 16

For the reaction,

N_{2} + 3 H_{2} \to 2 {NH}_{3}

, the rate of change of concentration for hydrogen is

0.3 \times 10^{- 4} {Ms}^{- 1}

. What will be the rate of change of concentration of ammonia?

HARD

12th ICSE

IMPORTANT

All In One ISC Chemistry Class 12>Chapter 19 - Sample Question Paper 4>SAMPLE QUESTION PAPER 4>Q 16

For a reaction between A and B, the initial rate of reaction is measured for various initial concentrations of $A$ and $B$ . The data provided is :

$[A]$	$[B]$	Initial rate $(mol L^{- 1} s^{- 1})$
$0.020$	$0.010$	$2.40 \times 10^{- 4}$
$0.020$	$0.030$	$2.16 \times 10^{- 3}$
$0.040$	$0.030$	$4.32 \times 10^{- 3}$