Statement I: In a zero-order reaction, the conc. versus time graph is a straight line

Statement II: The rate change of concentration per unit time in zero-order reaction remains constant

Statement I and statement II are correct and statement II is correct explanation of statement I

The correct answer is option 1. Statement I and statement II are correct and statement II is the correct explanation of statement I.

In a zero-order reaction, the rate of the reaction is independent of the concentration of the reactant(s). This means that even if you change the initial concentration of the reactant, the rate at which the reactant is consumed (or product is formed) remains constant.

The rate law for a zero-order reaction can be expressed as:

\(\text{Rate} = k \)

where \( k \) is the rate constant. This indicates that the rate of reaction is equal to the rate constant \( k \), and it When plotting the concentration of the reactant versus time (\([A]\) vs. \(t\)), the graph is a straight line with a negative slope.  The slope of this line is equal to \(-k\), indicating the rate of change of concentration per unit time.

Analysis of Statements:

Statement I: In a zero-order reaction, the concentration versus time graph is a straight line.

This statement is true. The reason behind this is that in a zero-order reaction, the concentration of the reactant decreases linearly with time at a constant rate. Therefore, when you plot \([A]\) versus \(t\), you get a straight-line graph.

Statement II: The rate change of concentration per unit time in a zero-order reaction remains constant.This statement is also true. In a zero-order reaction, the rate of reaction (\( \text{Rate} \)) is constant and is equal to the rate constant \( k \). This means that the amount of reactant consumed (or product formed) per unit time is constant throughout the reaction.

Relationship Between Statements: Statement II explains why Statement I is true. The constant rate of reaction (Statement II) directly leads to a straight-line graph of concentration versus time (Statement I). Since the rate of reaction is constant, the concentration of the reactant decreases uniformly over time, resulting in a linear relationship when plotted.

Conclusion:

Therefore, both statements are correct, and Statement II correctly explains why Statement I is true. The characteristics of zero-order reactions, including their rate independence from reactant concentration and the resulting straight-line graph of concentration versus time, align with these statements and their explanations.