NIOS Class 12 Chemistry Chapter 14 Chemical Kinetics Solutions English Medium As Per New Syllabus to each chapter is provided in the list so that you can easily browse throughout different chapters NIOS Class 12 Chemistry Chapter 14 Chemical Kinetics Notes in English and select need one. NIOS Class 12 Chemistry Solutions English Medium Download PDF. NIOS Study Material of Class 12 Chemistry Notes Paper Code: 313.
NIOS Class 12 Chemistry Chapter 14 Chemical Kinetics
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Chemical Kinetics
Chapter: 14
| Module – V: Chemical Dynamics |
INTEXT QUESTIONS 14.1
1. Which of the following units could be used to express the rate of reaction between magnesium and hydrochloric acid?
(a) cm⁻³ s
(b) cm³ min⁻¹
(c) cm³ s⁻¹
(d) mol dm⁻³ min⁻¹
Ans: (d) mol dm⁻³ min⁻¹
2. For the following reaction, 2NO₂(g) + F₂(g) ⎯⎯→ 2NO₂F(g) Write the expression for the average, rate of reaction in terms of :
(a) rate of formation of NO₂F
(b) rate of disappearance of NO₂
(c) rate of disappearance of F₂
(d) equivalent rate of formation of product and disappearance of reactants.
Ans: (i) ∆[N₂O F])/(∆t)
(ii) (-Δ[NO ])/(∆t)
(iii) (– [F₂ ])/(Δt)
(iv)1/2 ([NO₂F])/(Δt) = –½(Δ[NO₂])/(Δt)
= (–Δ[F₂])/(Δt).
3. Express the instantaneous rates of formation of product and disappearance of reactants for the above reaction.
Ans: ½(d [NO₂F])/(dt) = –1/2(d [NO₂])/(dt)
= (d [F₂])/(dt).
4. Explain why the reaction CO(g) + NO₂(g) → CO₂(g) + NO(g) occurs more slowly when the volume of the system is increased.
Ans: Increase in volume would decrease the pressure which would decrease the rate of reaction.
INTEXT QUESTIONS 14.2
1. The rate of a certain reaction, A → Product is 1.0 × 10⁻³ mol/litre. When conc. A = 0.020M, what is rate constant k, if the reaction is :
(a) zero order.
(b) first order.
Ans: (a) 1.0 × 10⁻³ mol litre⁻¹ s⁻¹
(b) 5.0 × 10⁻² s⁻¹
2. For the following reaction:
C₂H₄ (g) + I₂(g) → C₂H₄I₂(g)
the rate equation is:
rate = k [C₂H₄(g)] [I2(g)]³/²
(a) What is the order of reaction with respect to each reactant?
(b) What is the overall order of reaction?
(c) What is the unit of k, if concentrations are measured in mol dm⁻³?
Ans: (a) First order with respect to C₂H₄ and 1.5 with respect to I₂.
(b) The overall order of reaction is 2.5
(c) k = (sec⁻¹)/(mol⁻³ dm )³/² = mol⁻³/² dm⁹/²s⁻¹.
3. The first order rate constant for the decomposition of C₂H₅Cl at 700 K is 2.5 × 10⁻³ min⁻¹. If the initial concentration is 0.01 mol L⁻¹, calculate the time required for the concentration of C₂H₅Cl to drop to half of its original value.
Ans: (a) 2.5 × 10–3 (min–1) = (2.303)/(10 min) log₁₀(0.01 mol L⁻¹) × x
(b) When half of the sample is decomposed:
t₁/₂ = (0.693)/(2.5 × 10⁻³)min = 0.277 × 10³
min = 2.77 × 10² min.
INTEXT QUESTIONS 14.3
1. As a rough rule of thumb, the rates of many reactions double for every 10ºC rise in temperature? Explain.
Ans: 10.
2. The rate constant of a reaction at 288 K is 1.3 × 10⁻⁵ litre/mol. While at 323K its rate constant is 8.0 × 10⁻³ lit./mol. What is the Ea for the reaction?
Ans: 34.0 K cal mol–1.
3. The rate of the reaction triples when temperature changes from 293 K to 323 K. Calculate the energy of activation for such a reaction.
Ans: 28.82 kJ.
4. H₂(g) and O₂(g) combine to form H₂ O(l) by an exothermic reaction. Why do they not combine when kept together for any period of time.
Ans: Molecules do not have enough energy to be equal to threshold energy.
5. What is an effective collision?
Ans: Collision is a collision between reactant molecules that results in a chemical reaction, leading to the formation of products. For a collision to be effective, it must meet two key criteria: sufficient energy (at least equal to the activation energy) and proper orientation of the colliding molecules.
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