Reaction Rate

A chemical reaction involves the chemical transformation of reactants into products. As the reaction progresses, the concentration of reactants decreases while the concentration of products increases. This variance in concentrations of reactants and products can be plotted in a graph as a function of time.

The speed at which a reaction progresses is called the reaction rate. It measures the rate of reactants’ disappearance or the rate of products’ appearance and is expressed in units of molarity-per-second.

The average reaction rate can be calculated from the change in concentrations of reactants or products during a specific period of time. The molar concentration value is denoted in brackets, t stands for the period of time, and the delta symbol represents ‘change in’.

Since reactants are depleted during a chemical reaction, the value of concentration change of reactants is always negative. Therefore, a reaction rate calculated in terms of reactants is supplemented by a negative sign, to make the overall value positive.

The reaction rate is not uniform throughout a reaction. The rate at the start of the reaction, at ‘time-zero’, is called the initial reaction rate. As the concent