Match List I with List II
| List I | List II |
| A. Linear plot with +ve slope and an intercept | I. \(t_{1/2}\) vs \(\frac{1}{[A]_0}\) for 2nd order |
| B. Linear plot with -ve slope and an intercept | II. \(t_{1/2}\) vs \([A]_0\) for 1st order |
| C. Linear horizontal plot | III. \(\frac{1}{[A]}\) vs time for the 2sn order |
| D. Linear plot passing through the origin | IV. Conc. \([A]\) vs time for zero order |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is option 3. A-III, B-IV, C-II, D-I.
| List I | List II |
| A. Linear plot with +ve slope and an intercept | III. \(\frac{1}{[A]}\) vs time for the 2nd order |
| B. Linear plot with -ve slope and an intercept | IV. Conc. \([A]\) vs time for zero order |
| C. Linear horizontal plot | II. \(t_{1/2}\) vs \([A]_0\) for 1st order |
| D. Linear plot passing through the origin | I. \(t_{1/2}\) vs \(\frac{1}{[A]_0}\) for 2nd order |
Let us delve into the details of each match in the context of chemical kinetics.
A. Linear plot with +ve slope and an intercept: III. \(\frac{1}{[A]}\) vs time for the 2nd order
For a second-order reaction, the integrated rate law can be expressed as:
\(\frac{1}{[A]} = kt + \frac{1}{[A]_0}\)
Here:
\([A]\) is the concentration of the reactant at time \(t\),
\(k\) is the rate constant,
\([A]_0\) is the initial concentration of the reactant.
This equation is of the form \(y = mx + c\), where:
\(y = \frac{1}{[A]}\),
\(x = t\),
the slope \(m = k\) (which is positive for a second-order reaction),
the intercept \(c = \frac{1}{[A]_0}\).
A plot of \(\frac{1}{[A]}\) vs. \(t\) will give a straight line with a positive slope \(k\) and an intercept equal to \(\frac{1}{[A]_0}\).

B. Linear plot with -ve slope and an intercept: IV. Conc. \([A]\) vs time for zero order
In a zero-order reaction, the concentration of the reactant \([A]\) decreases linearly with time. The rate of the reaction is independent of the concentration of the reactant, and the equation for a zero-order reaction can be expressed as:
\([A] = [A]_0 - kt\)
Where:
\([A]\) is the concentration of the reactant at time \(t\).
\([A]_0\) is the initial concentration of the reactant.
\(k\) is the rate constant (with units of concentration/time).
\(t\) is the time.
This equation represents a straight line with:
A negative slope equal to \(-k\).
A y-intercept equal to \([A]_0\).
The linear plot of \([A]\) vs. time will have a downward (negative) slope, indicating the decrease in concentration over time.

C. Linear horizontal plot: II. \(t_{1/2}\) vs \([A]_0\) for 1st order
For a first-order reaction, the half-life \(\left(t_{1/2}\right)\) is independent of the initial concentration \([A]_0\). The formula for the half-life of a first-order reaction is:
\(t_{1/2} = \frac{0.693}{k}\)
Here, \(t_{1/2}\) is the half-life, and \(k\) is the rate constant. Since \(t_{1/2}\) does not depend on \([A]_0\), a plot of \(t_{1/2}\) versus \([A]_0\) for a first-order reaction will be a horizontal line, indicating that \(t_{1/2}\) remains constant regardless of the initial concentration.

D. Linear plot passing through the origin: I. \(t_{1/2}\) vs \(\frac{1}{[A]_0}\) for 2nd order
For a second-order reaction, the half-life \(\left(t_{1/2}\right)\) is inversely proportional to the initial concentration \(\left([A]_0\right)\). The formula for the half-life of a second-order reaction is:
\(t_{1/2} = \frac{1}{k[A]_0}\)
Here:
\(t_{1/2}\) is the half-life,
\(k\) is the rate constant,
\([A]_0\) is the initial concentration of the reactant.
This equation can be rewritten as:
\(t_{1/2} = \frac{1}{k} \times \frac{1}{[A]_0}\)
This is of the form \(y = mx\), where:
\(y = t_{1/2}\),
\(x = \frac{1}{[A]_0}\),
and the slope \(m = \frac{1}{k}\).
A plot of \(t_{1/2}\) versus \(\frac{1}{[A]_0}\) for a second-order reaction will be a straight line that passes through the origin, with the slope equal to \(\frac{1}{k}\).
Thus, the correct matching is option 3: A-III, B-IV, C-II, D-I.