In a first-order reaction, the reaction rate is directly proportional to the concentration of one of the reactants. This means that if the concentration of the reactant is doubled, the reaction rate will also double. The relationship between the reaction rate and the concentration of the reactant can be represented by the following rate law equation:Rate = k[A]^1where Rate is the reaction rate, k is the rate constant, and [A] is the concentration of the reactant.Experimental evidence supporting this relationship can be found in numerous studies. One classic example is the hydrolysis of ethyl acetate, a first-order reaction. In this reaction, ethyl acetate CH3COOC2H5 reacts with water H2O to form acetic acid CH3COOH and ethanol C2H5OH :CH3COOC2H5 + H2O CH3COOH + C2H5OHTo study the effect of changing the concentration of ethyl acetate on the reaction rate, a series of experiments can be performed with varying initial concentrations of ethyl acetate while keeping the concentration of water constant. The reaction rate can be monitored by measuring the formation of acetic acid or ethanol over time.The results of these experiments would show that the reaction rate increases linearly with the increase in the concentration of ethyl acetate. This linear relationship confirms that the reaction is first-order with respect to ethyl acetate.In conclusion, the change in concentration of reactants in a first-order reaction directly affects the reaction rate. Experimental evidence, such as the hydrolysis of ethyl acetate, supports this relationship, demonstrating that the reaction rate increases linearly with the increase in the concentration of the reactant.