NEET · Chemistry · STD 12 - 3. Chemical kinetics

If the rate constant of a reaction is \(0.03 s^{-1}\), how much time does it take for \(7.2 mol L ^{-1}\) concentration of the reactant to get reduced to \(0.9 mol L ^{-1}\) ?
(Given : \(\log 2=0.301\) )

A 69.3 s
B 23.1 s
C 210 s
D 21.0 s

Verified Solution

Answer & Solution

Correct Answer

(A) 69.3 s

Step-by-step Solution

Detailed explanation

\(\begin{array}{l} K =0.03 s^{-1} \text { (First order reaction) } \\ A _0=7.2 mol L ^{-1} \\ A_{ t }=0.9 mol L ^{-1} \\ 7.2 \xrightarrow{ t _{1 / 2}} 3.6 \xrightarrow{ t _{1 / 2}} 1.8 \xrightarrow{ t _{1 / 2}} 0.9 \\ t =3 t _{1 / 2}=\frac{3 \times 0.693}{0.03}=69.3 s\end{array}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From NEET

Explore more questions on app

(a) Pure nitrogen	(i) Chlorine
(b) Haber process	(ii) Sulphuric acid
(c) Contact process	(iii) Ammonia
(d) Deacon's process	(iv) Sodium azide or Barium azide

If the rate constant of a reaction is \(0.03 s^{-1}\), how much time does it take for \(7.2 mol L ^{-1}\) concentration of the reactant to get reduced to \(0.9 mol L ^{-1}\) ?(Given : \(\log 2=0.301\) )

Step-by-step Solution

If the rate constant of a reaction is \(0.03 s^{-1}\), how much time does it take for \(7.2 mol L ^{-1}\) concentration of the reactant to get reduced to \(0.9 mol L ^{-1}\) ?
(Given : \(\log 2=0.301\) )