# NCERT Class 12 Chemistry Competitive Exams Questions and Answers NCERT Class 12 Chemistry QUESTIONS

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## CHEMICAL KINETICS

1. The Arrhenius equation is
(a) K= Ae Ea/RT
(b) K=e -Ea/ RT
(c) K- Ae -Ea/RT
(d)K= Ae -Rt/ Eà
2. Considering an exothermic reaction, with activation energy Eà and Éà for the forward and backward reaction respectively, Now we can say
(a) Eà=Éa
(b) Eà> Éa
(c) E <Éa
(d) can’t be predicted which is more
3. When log K is plotted Vs for a 1st order reaction we get a straight line. The slope of the line is equal to

(a)-(Ea/ 2.303R)
(b)-(Ea/R)
(c) -(2.303R/Ea)
(d)-(Ea/ 2.303)

1. For a reaction K = 2×10–² mole lit–¹sec–¹ If the concentration of the reactant is 1M, the half life
period of the reaction is

(a) 20 sec
(b) 25 sec
(c) 34.6 sec
(d) 50 sec
2. The rate of a reaction A→ product, increases by a factor of 100, when conc. of A is increased 10 fold. The order of the reaction is
(a) 3
(b) 2
(c) 1
(d) 0.5
3. The rate constant of a reaction is 2 x 10–⁵ sec–¹ If the initial concentration is 0.1 M, the initial rate
(a) 2x 10–⁴ M sec–¹
(b) 2 x 10–⁵ M sec-¹
(c) 2x 10–⁶ M sec –¹
(d) 2 x 10–⁷ M sec–¹
4. For a 1st order reaction, the time required for 99.9% completion is
(a) ten times the time required for half completion of reaction
(b) three times the time required for 90% completion of reaction
(c) five times the time required for 75%completion of reaction
(d) all are correct
5. The half life period for a 1st order reaction is 6,93 sec. its rate constant is
(b) 100 sec-¹
(a) 10 sec–¹
(d) 1 sec–¹
(c) 0.1 sec-¹
6. Alkaline hydrolysis of ester is an example of
(a)1st order reaction
(b) 2nd order reaction
(c)zero order reaction
(d)pseudo 1st order reaction
7. The rate of a reaction depends upon
(a) concentration of reactant
(b) temperature
(d) all of these
(c) catalyst
8. The rate constant of a reaction depends upon
(b) catalyst
(a) temperature
(c) nature of reactant
(d) all of these
9. For a reaction, H²0² →H²O + ½0²
• d[H²O²]
( ————)= – K¹[H²O²],
d
t

d[H²O²]. d[O²]
—— = K²[H²0²], ——- = K³[H²O²]
dt dt

The relation between K, K, and K, is
(b) K¹ =K² = 2K³
(a) K¹ = K² =K³
(c) 2K¹= 4K² =K³
(d) 2K¹= 2K² =K³

1. The rate constant of a reaction is independent of
(b) catalyst
(a) temperature
(c) conc. of reactant
(d) none of these
2. The unit of rate constant for 2nd order reaction is
(a) mole lit–¹ sec- ¹
(b) mole–¹ lit–¹sec–¹
(c) mole–¹ lit–¹ sec–¹
(d) mole–² lit–² sec–¹
3. If the rate of formation of NH, for the reaction N²+3H² → 2NH³ is 2 x 10⁴ Msec–¹ the rate or disappearance of hydrogen is
(a) 1x 10–⁴ M sec –¹
(b) 2x 10–⁴ M sec–¹
(c) 3×10–⁴ M sec–¹
(d) 6x 10–⁴ M sec–¹
4. The half life period for a zero order reaction is equal to

(a) 0.693/k
(b) a /2k
(c) 1/ka
(d) a/k

1. For a 1st order reaction log K is plotted against 1/T and, the slope of the line is 1.5×10²K. The activation energy for the reaction would be
(a) 2872 J mole–¹
(b) 28.72J mole–¹
(c) 1914 J mole–¹
(d) 1200 J mole–¹
2. Which of the following statements regarding molecularity is wrong?
(a) it is the number of reactant molecules colliding in a single step of chemical reaction.
(b) it refers to individual step of the reaction.
(c) it may be whole number or fractional
(d) the rate of reaction is independent of molecularity.
3. For a chemical change 2A +3B→ Product’s the rates w.r.t. ‘A’ is r, and w.r.t. ‘B’ is r² The rates, r¹
and r² are related as

(a) r¹=r²
(6) 2r¹= 3r²
() 3r¹-2r²
(d)r¹ = 3r²
4. The rate constant for the reaction 2N²O⁵→ 2N²O⁴+0² is 3 x 10–⁵ sec–¹ If the rate is 2.4 x 10-⁵ M sec–¹ the concentration of N²O⁵ is
(a) 1.4 M
(b) 0.04M
(c) 1.2 M
(d) 0.8 M
5. Write two factors which influence the rate of reaction.
(b) Concentration of reactant and temperature.
(a) fusel
(c) Margo
(d) on the basic level of kinetic energy
6. Which equation gives relationship between rate constant and temperature?
(a) Ostwald’s equation
(b) Khichoff’s equation
(c) Arrhenius equation
(d) Nernst equation
7. At 25°C the half life of decomposition of H²O² is 50 min. If initially 4M H,O, is present, amount of H²O² left after 200 min is
(b) 0.5 M
(a) 2M
(d) 1 M
(c) 0.25M
8. The rate constant is numerically same for three reactions of 1st, 2nd and 3rd order respectively. If conc–¹ of the reactant is more than 1M, which one is true for the rates of the three reactions ?
(b) r¹ T³r< (a) r1=R2=r3 (b) r 1r2>r3 (d) none of these
9. In the above question if conc. of the reactant is less
than 1 M, then

(b) r²T3>d (a) r1=R2=r3 (b) r 1r2>r3 (d) none of these
10. A reaction X-product, completed 50% in 25min. If concentration of ‘X’ is doubled, 50% completed in 50 min, the order of the reaction is
(b) 1
(a) 0
(d) 3
(c) 2
11. A reaction involving two different reactants can never be
(b) unimolecular reaction
(a)first order reaction
(c) second order reaction
(d) bimolecular reaction
12. A substance with half life period 4 days is taken to another place in 12 days. The amount of substance
left now is

(a)12
(b)8
(d)9
(c)16
13. For every 10°C rise in temperature the rate of
reaction increases nearly

(a) 10 times
(b) 2 times
(c) 5 times
(d) 8 times
14. The reaction CH⁶COOC³ H² + H²0H CH³ COOH +C²H³-OH is an example of
(a) zero order reaction
(b) 1st order reaction
(c) 2nd order reaction
(d) fractional order reaction
15. For a 1st order reaction log (a – x) is plotted Vs time, a straight line is obtained with slope
(a)K/2.303
(a)-k/2.303
(c) -k/-2.303–¹
(d)-2.303 K
16. The rate constant of a reaction is 2.5 x 10–⁵ mole–⁸ lit–¹sec–¹. The order of the reaction is
(a) zero
(b) 1st
(c) 2nd
(d) 3rd
17. For a reaction, A- B+C, activation energy is 15 kJ/mole and enthalpy of reaction is +5kJ/mole. The activation energy for the reaction B+CA is
(a) 10 kJ/mole
(b) 20 kJ/mole
(c) 30 kJ/mole
(d) 15 kJ/mole
18. For the reaction A B +C, AH =+25 kJ mole–¹ The activation energy for the reaction is
(a) 25 kJ/mole
(b) less than 25 kJ/mole
(c) more than 25 kJ/mole
(d) none of these
19. A catalyst has no effect on
(a) rate of forward reaction
(b) activation energy
(c) thershold energy
(d) heat of reaction
20. Inversion of Cane Sugar is an example of —– order reaction.
(c) Pseudofirst
(a) hesi
(b) malo
(d) geindergi
21. The rate of reaction at different times are as follows time (sec–¹)10 20 30 rate (M sec–¹) 1.5×10–2 1.48×102 1.51×102 1.49×10 The reaction is
(a) zero order
(b) 1st order
(c) 2nd order
(d) 3rd order
22. For a chemical reaction A B, it is found that the rate of reaction doubles when the conc. of A’ is increased four times. The order of reaction is
(a) 0
(b) 0.5
(c) 1
(d) 2
23. The unit of rate constant for zero order reaction is
(b) mole lit–¹sec–¹
(a) sec–¹
(d) mole–¹lit–¹sec–¹
(c) mole–¹lit sec–¹
24. For a gascous reaction the rate = K[A]B]. The volume of the vessel containing the gas is suddenly reduced to th of the initial volume. The rate of reaction relative to initial rate would be
(b) 16
(a)1/16
(d)same
(c) 8
25. The half life period for a 1st order reaction is 10 min. The initial amount of the reactant was 0.08 M and concentration at any instant is 0.01 M. The time taken for the reaction is
(b) 20 min
(a) 10 min
(d) 40 min
(C) 30 min
26. A large increase in rate of reaction for a rise of temperature is due to
(a) increase in number of molecular collisions.
(b) increase in number of activated molecules.
(c) decrease in activation energy
(d) lowering of threshold energy