Concentration data is commonly monitored during a reaction to determine the order with respect to a reactant. Consider the types of observations listed, and determine which order is likely for that reactant. Assume all other factors are held constant. The reaction rate increases in direct proportion to the concentration of the reactant in solution.
1. An increase in the concentration of the reactant in solution causes the reaction rate to increase exponentially.
a. first order.
b. second order.
c. zero order.
2. The reaction rate is constant regardless of the amount of reactant in solution.
a. first order.
b. second order.
c. zero order.
3. The reaction rate increases in direct proportion to the concentration of the reactant in solution.
a. first order.
b. second order.
c. zero order.

For a first order reaction, the concentration of the reactants varies exponentially with the rate of reaction. The curve of a first order reaction shows an exponential relationship between the rate of reaction and the change in the concentration of reactants.

For a zero order reaction, the rate of reaction is independent of the concentration of the reactants. So, regardless of the amount of reactant in solution, the rate of reaction is constant.

For a second reaction, the reaction rate increases in direct proportion to the concentration of the reactant in solution.