Question

For a 1 st order reaction, if the concentration is doubled then the rate of reaction becomes:
A. Double
B. Half
C. Four times
D. Remain same

Answer 1

Hint: Rate equation tells the relation between the rate of the equation and concentration of the reactants. This equation is different for different orders of equations. Here the equation for first order is required.

Step by step answer: To know this answer we need to know what first order reaction is, rate and concentration. So, first order reaction is a reaction that proceeds at a rate that depends linearly on one reactant concentration. The equation stating first order kinetics is as given below.
\[Rate = \dfrac{{d[A]}}{{dt}} = k[A]\]
Here, rate is the reaction rate and k is the reaction rate coefficient whose unit is 1/time. However, the values of k vary for non-first order reactions. When the concentration of a reactant is doubled then the rate also doubles. According to the formula,

\[Rate = k[A]\]

So, when A will double the rate will also double. Therefore, the correct option is A.

Additional information: The order of reaction is the relationship between rate of the reaction and concentration of the compounds which are part of it. The rate of first order reaction is dependent mainly on the concentration of one species in the reaction.
There are 4 types of order of reaction which are zero order, first order, Pseudo first order and second order reaction. In zero order reaction, the rate of reaction is independent of concentration of reactants. In first order rate depends on only one reactant. In Pseudo first order, the concentration of one reactant remains constant and is therefore included in the rate constant in the rate expression. In a second order reaction either concentration of one reactant is squared or from two separate reactants.

Note: The four types of order of reactions naming zero, first pseudo-first and second order reactions are applied on different chemical reactions based on the reactants and each order of reaction has a different equation for finding rate.