For a chemical reaction R → P, rate of reaction is given by

Correct Answer: (C) -Δ[R]/Δt

For a chemical reaction $\text{R}\to \text{P}$$\text{R}$ $\rightarrow$ $\text{P}$, reactant concentration decreases with time. Therefore, the rate of reaction is expressed in terms of reactants as $-$$\Delta[R]$/$\Delta$ t.