Title DPP - 3 Solutions.pdf ✅

Class : XIIth Subject : CHEMISTRY Date : DPP No. : 3 1 (c) K1 = 1016e ―2000/T;K2 = 1015e ―1000/T if K1 = K2 then 1016e ―2000/T = 1015e ―1000/T or log 10 ― 2000 T = ― 1000 T or T = 1000 2.303 K 2 (c) As we know that, rate of reaction is directly proportional to concentration of reactant and inversely proportional to the volume of vessel. i.e.,concentrationα ∝ n v For a given reaction, 2NO(g) + O2(g)⇌2NO2(g) Rate of reaction=k[NO] 2 [O2] If volume of vessel is reduced by 1 3 rd of its initial value, then concentration of compound is increase by 3 times. Hence, the rate of reaction will be increased by 27 times. 3 (c) For a zero order reaction k0 = [A0] 2t1/2 Since,[A]0 = 2 M,t1/2 = 1 h So, k0 = 1 and k0 = ∆x t or t = 0.50 ― 0.25 1 = 0.25 h 4 (c) A + B→C + D Rate (r)=k[A] a [B] b ...(i) 2r=k[2A] a [B] b ...(ii) 3r=k[A] a [9B] b ...(iii) Dividing eq.(ii) by eq.(i) 2 = 2 a or a=1 Dividing eq (iii)by eq.(i) 3 = 9 b or 3 = 3 2b or 2b = 1 or b = 1/2 So order of reaction = 1 + 1 2 = 3 2 Topic :- Chemical Kinetics Solutions
5 (a) N = N0 2 n n = T t1/2 = 40 20 = 2 ∴ N = N0 2 2 = N0 4 6 (a) p1 = 80 kPa , (t1/2)1 = 350s p1 = 40 kPa , (t1/2)1 = 175s 80 40 = 350 175 = 2 ∵ p1 p2 = (t1/2)1 (t1/2)2 = a1 a2 (t1/2) ∝ a(zero order reaction) 7 (b) Thermal decomposition, CH3CHO ∆ CH4 + CO dx dt = k[CH3CHO] 3/2 8 (b) For the reaction : A→ 2B + C p1 0 0 After 10 min p1 ―p 2p p After long time 0 2p1 p1 Total pressure = (p1 ― p + 2p + p) = 176 mm Total pressure after long time = 2p1 + p1 = 270 mm Calculate the value of p from above two equation and then the difference of p1 and p will be the pressure of A 9 (c) Zero order reaction t1/2 Concentration
Where, Ea = activation energy of forward reaction E′′a=activation energy of backward reaction The above energy profile diagram shows that Ea > E′′a The potential energy of the product is greater than that of the reactant, so the reaction is endothermic. Ea = E′′a + ∆E Et = Ea or Et > E′′a 10 (d) Combination of H2and Br2 to give HBr is zero order reaction as the rate of reaction is not affected by the concentration of reactants. H2 + Br2 hv 2HBr 11 (a) Rate of reaction = 1 4 d(NO2 ) dt = 5.2 × 10―3 4 × 100 = 1.3 × 10―5 Ms ―1 12 (d) 9 = ( 3.24 × 10―2 1.2 × 10―3 ) n 9 = (3 3 ) 2/3 order of the reaction is=2/3 13 (b) For zero order reaction k = a 2t1/2 = a 2 × 100 = a 200 When 80% completion take place Reaction coordinate E 200 kJ B E'a Ep (energy of product) E energy of the reaction A E ER (en erg y of rea cti on) threshold energy (Et) Ea
k = x t a 200 = 0.80a t t = 200 × 0.8 = 160 min 14 (a) 2A + B→product [B] is doubled, half-life didn’t change Half-life is independent of change in concentration of reactant i.e., first order First order w.r.t. to B When [A] is doubled, rate increased by two times ⇒ First order w.r.t.A Hence, net order of reaction =1+1=2 Unit for the rate constant=conc. (1―n)t ―1 = (mol ―1 ) ―1 .s ―1 L. mol ―1 s ―1 16 (c) H2O + O⟶2OH; ∆H = 72kJ at 500 K; Given Ea = 77 kJmol―1 2OH⟶H2O + O;EaB.R. For a reaction EaF.R = ∆H + EaB.R ∴ 77 = 22 + EaB.R ∴ EaB.R = 5kJ mol―1 17 (d) According to Arrhenius equation, the relationship between the activation energy and temperature is k = Ae ―Ea/RT log k = ― Ea 2.303 RT + logA ∴ Activation energy decreases with rise in temperature, thereby increasing the rate of the reaction. 18 (d) rate = K[A] 1 K = 2.0 × 10―5 0.01 = 2.0 × 10―3 s ―1 ∴ t1/2 = 0.693 2 × 10―3 = 347s 19 (c) For a zero order reaction, the plot of concentration of reactant vs time is a straight line (linear) with a negative slope and non-zero intercept.