For 2nd order reaction, changes with time:

Explanation

Option C, "Rate, t1/2," is correct for a second-order reaction.In a second-order reaction, the rate of the reaction is directly proportional to the square of the concentration of the reactant. This means that as the concentration of the reactant decreases over time, the rate of the reaction will also decrease.The half-life (t1/2) of a reaction is the time it takes for half of the initial concentration of the reactant to be consumed. In a second-order reaction, the half-life is inversely proportional to the initial concentration of the reactant. As the concentration decreases, the half-life increases. This is because with fewer reactant molecules, it takes longer for the reaction to proceed and reach the halfway point.Options A, B, and D are incorrect because they do not describe the specific relationship between the variables in a second-order reaction. The rate constant (k) and the reaction order remain constant throughout the reaction, while the rate and half-life change with time due to the decreasing concentration of the reactant.