Question

Match the rate law given in column I with the dimensions of rate constants given in column II and mark the appropriate choice.

Column I		Column II
$(A)$	Rate $=k[NH_{3}]^{0}$	(i)	$mol\, L^{-1} s^{-1}$
(B)	Rate $=k[H_{2}O_{2}] [I^{-}]$	(ii)	$L\, mol^{-1} s^{-1}$
(C)	Rate $=k[CH_{3}CHO]^{3/2}$	(iii)	$s^{-1}$
(D)	Rate$=k[C{_2}H_{5}Cl]$	(iv)	$L^{1/2} mol^{-1/2} s^{-1}$

• A. $(A) \to (iv), (B) \to (iii), (C) \to (ii), (D) \to (i)$
• B. $(A) \to (i), (B) \to (ii), (C) \to (iii), (D) \to (iv)$
• C. $(A) \to (ii), (B) \to (i), (C) \to (iv), (D) \to (iii)$
• D. $(A) \to (i), (B) \to (ii), (C) \to (iv), (D) \to (iii)$

Answer 1

Answer: (D)

(A) Rate $= k \left[ NH _{3}\right]^{0}$
It is zero order reaction.
$\therefore $ Units of rate constant are same as rate.
i.e $mol\,l ^{-1} s ^{-1}$
(B) Rate $= k \left[ H _{2} O _{2}\right]^{1}\left[ I ^{-}\right]^{1}$
It is second order reaction as order $=1+1=2$
$\therefore $ Units of Rate constant are $L mol ^{-1} s ^{-1}$
(C) Rate $= k \left[ CH _{3} CHO \right]^{3 / 2}$
It is fractional order reaction with order $=\frac{3}{2}$
$\therefore $ Units of rate constant are $L^{\frac{1}{2}} mol ^{-\frac{1}{2_s^{-1}}}$
(D) Rate $= k \left[ C _{2} H _{5} Cl \right]^{-1}$
It is first order reaction. So units of rate constant are $s ^{-1}$