Tiêu đề DPP - 7 Solutions.pdf ✅

Class : XIIth Subject : CHEMISTRY Date : DPP No. : 7 1 (d) If Ea = 0, k = Ae ―Ea/RT = Ae 0 = A Hence, k becomes independent of T 2 (b) Larger is surface area, more is rate of reaction. 3 (c) Reactions having lower energy of activation occurs more fast under similar experimental conditions. 4 (b) For the first order reaction Rate( dx dt) = k[A] [A]→concentration of reactant K→rate constant Given that, dx dt = 1.5 × 10―2mol L ―1min―1 K=? and [A]=0.5 M 1.5 × 10―2 = k × 0.5 k = 1.5 × 10―2 0.5 =3 × 10―3min―1 For first order reaction, Half-life period t1/2 = 0.693 k = 0.693 3 × 10―2 =23.1min 5 (b) Temperature coefficient, = kt + 10 kt 2 = 10―3 kt kt = 10―3 2 = 10 × 10―4 2 = 5 × 10―4 Topic :- Chemical Kinetics Solutions
6 (d) The minimum energy required by reaction molecules to undergo reaction is called activation energy. 7 (c) For an nth order reaction t1/2 ∝ 1 a n―1 For 1st order reaction ,t1/2 ∝ 1 a 1―1 ∝ a 0 8 (c) For every 10°C rise of temperature, rate is doubled. Thus, temperature coefficient of the reaction=2 When temperature is increased by 50°C, rate becomes =2 50/10 = 2 5 times=32 times 9 (d) Order may or may not be equal to molecularity. 10 (c) Use r = K[A]m[B] n 11 (c) The reaction occurring in two steps has two activation energy peaks. The first step, being fast needs less activation energy. The second step being slow, needs more activation energy. Therefore, second peak will be higher than the first 13 (d) r1 = K[A] 1 ; r2 = K[A] 2 , r3 = K[A] 3 if [A] > t; r3 > r2 > r1 14 (c) t = 2.303 k log a (a ― x) If t = t1/4; x = a/4 ∴ t1/4 = 2.303 k log a (a ― 1/4) 2.303 k log 4 3 15 (a) K = Ae ―Ea/RT 16 (c) 100 2 days 50 50 4 days 25 25 8 days 12.5 Hence, the order of reaction is second. For second order reaction, k = 1 2 [ x a(a ― x)] = 1 2 [ 50 100 × 50]
= 1 200 t1/2 = 1 k.a ⇒ = 1 1/200.100 = 200 100 = 2days 17 (b) 1 3 d[Br2] dt = ― 1 5 d[Br―] dt 18 (d) The reaction is said to be of second order if its reaction rate is determined by the variation of two concentration terms of reactants. CH3COOCH3 + NaOH→CH3COONa + H2O Is an example of second order reaction. 19 (b) Temperature coefficient is the ratio of two velocity constant having the difference of 10°C. For most of the reaction the value of temperature coefficient lies between 2 and 3
ANSWER-KEY Q. 1 2 3 4 5 6 7 8 9 10 A. D B C B B D C C D C Q. 11 12 13 14 15 16 17 18 19 20 A. C C D C A C B D B C