The correct answer is 'decreases.' Explanation & Key Takeaways: • With the progress of any chemical reaction, the rate of the chemical reaction decreases with time. • The rate of a reaction decreases as time progresses. • As a reaction progresses the reactants are being turned into products, so the number of reactant particles left is decreasing. Related Concepts: • The rate of reaction refers to the speed at which the products are formed from the reactants in a chemical reaction. • For example, the reaction rate of the combustion of cellulose in fire is very high and the reaction is completed in less than a second. • The rate of reaction or reaction rate is the speed at which reactants are converted into products. • Some chemical reactions are nearly instantaneous, while others usually take some time to reach the final equilibrium. • Factors Affecting the Rate of Reaction • The rate of reaction highly depends on the type and nature of the reaction. • The physical state of reactants, number of reactants, complexity of reaction, and other factors highly influence the reaction rate as well. • The rate of reaction is generally slower in liquids when compared to gases and slower in solids when compared to liquids. • The size of the reactant also matters a lot. The smaller the size of the reactant, the faster the reaction. • Pressure increases the concentration of gases which in turn results in the increase of the rate of reaction. • The reaction rate increases in the direction of fewer gaseous molecules and decreases in the reverse direction. • Thus, it can be understood that pressure and concentration are interlinked and that they both affect the rate of reaction. • The rate of reaction also depends on the type of solvent. Properties of solvent and ionic strength highly affect the reaction rate. • The order of reaction manages how the reactant pressure or concentration affects the rate of reaction.