Match List-I with List-II.
| List-I (Reaction and order asked) | List-II (Order from the experimental rate law) |
|---|---|
| (A) \( \ce{CHCl3 + Cl2 -> CCl4 + HCl} \): overall order | (I) 0 |
| (B) \( \ce{2NO(g) + O2(g) -> 2NO2(g)} \): overall order | (II) 3/2 |
| (C) \( \ce{2H2O2 -> 2H2O + O2} \) (catalysed by I− in an alkaline medium): order with respect to H2O2 | (III) 1 |
| (D) \( \ce{C2H4(g) + H2(g) -> C2H6(g)} \): order with respect to H2 | (IV) 3 |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → A-II, B-IV, C-III, D-I
The order with respect to a reactant is the power of its concentration in the experimental rate law, and the order of the whole reaction is the sum of these powers. A reactant whose concentration does not appear in the rate law has the power zero. The four rate laws are:
\( \displaystyle \ce{CHCl3 + Cl2 -> CCl4 + HCl} \qquad \text{Rate} = k[\ce{CHCl3}][\ce{Cl2}]^{1/2} \)
\( \displaystyle \ce{2NO(g) + O2(g) -> 2NO2(g)} \qquad \text{Rate} = k[\ce{NO}]^2[\ce{O2}] \)
\( \displaystyle \ce{2H2O2 -> 2H2O + O2} \qquad \text{Rate} = k[\ce{H2O2}][\ce{I^-}] \)
\( \displaystyle \ce{C2H4(g) + H2(g) -> C2H6(g)} \qquad \text{Rate} = k[\ce{C2H4}] \)
(A) Order of the whole CHCl3 reaction — This matches (II) 3/2: 1 + 1/2, though both coefficients are one.
(B) Order of the whole NO reaction — This matches (IV) 3: 2 + 1; here the powers are the same as the coefficients.
(C) Order with respect to H2O2 — This matches (III) 1; [H2O2] has the power one, though its coefficient is two.
(D) Order with respect to H2 — This matches (I) 0; [H2] does not appear in the rate law, so the rate does not depend on it.
NCERT (2026-27 edition):
3.2.2 Rate Expression and Rate Constant – “Some other examples are given below:”
\( \displaystyle 1.\ \ce{CHCl3 + Cl2 -> CCl4 + HCl} \qquad \text{Rate} = k[\ce{CHCl3}][\ce{Cl2}]^{1/2} \)
“Hence, the rate equation for this reaction will be Rate = k [NO]2[O2]”
3.2.3 Order of a Reaction – “Sum of these exponents, i.e., x + y in (3.4) gives the overall order of a reaction whereas x and y represent the order with respect to the reactants A and B respectively.”
3.2.4 Molecularity of a Reaction – “Consider the decomposition of hydrogen peroxide which is catalysed by iodide ion in an alkaline medium.” … “This reaction is first order with respect to both H2O2 and I–.”
3.3.2 First Order Reactions – “Hydrogenation of ethene is an example of first order reaction.”
\( \displaystyle \ce{C2H4(g) + H2(g) -> C2H6(g)} \qquad \text{Rate} = k[\ce{C2H4}] \)