Question

For a chemical reaction R → P, the variation in the concentration (R) vs. time (t) plot is given as:

(i) Predict the order of the reaction.

(ii) What is the slope of the curve?

(iii) Write the unit of rate constant for this reaction.

Answer 1

For a chemical reaction R→P, the variation in the concentration (R) vs. time (t) plot is given as follows:

(i) The order of the reaction zero.

(ii) Slope = -k

Answer 2

(i) Predict the order of the reaction

The graph shows a straight line when concentration of reactant R is plotted against time t.

[R] = [R]₀ ​− kt

Since the plot is a straight line with a negative slope, the reaction is zero order.

(ii) Slope of the curve

From the zero-order equation:

[R] = [R]₀​ − kt

The slope of the [R] vs t graph is −k (negative of the rate constant).

(iii) Unit of rate constant

For a zero-order reaction:

Rate = k

Rate has units of concentration/time.

If concentration is in mol L⁻¹ and time in seconds:

Unit of k = mol L⁻¹s⁻¹