Rates of Reaction Example Problem

This example problem demonstrates how to use reaction rates to determine the coefficients of a balanced chemical equation. Problem The following reaction is observed:2A bB → cC dDAs the reaction progressed, the concentrations changed by these ratesrateA 0.050 mol/LÂ ·srateB 0.150 mol/LÂ ·srateC 0.075 mol/LÂ ·srateD 0.025 mol/LÂ ·sWhat are the values for the coefficients b, c, and d? Solution Chemical reaction rates measure the change in concentration of the substance per unit time.The coefficient of the chemical equation shows the whole number ratio of materials needed or products produced by the reaction. This means they also show the relative reaction rates.Step 1:Â  Find brateB/rateA b/coefficient of Ab coefficient of A x rateB/rateAb 2 x 0.150/0.050b 2 x 3b 6For every 2 moles of A, 6 moles of B are needed to complete the reactionStep 2:Â  Find crateB/rateA c/coefficient of Ac coefficient of A x rateC/rateAc 2 x 0.075/0.050c 2 x 1.5c 3For every 2 moles of A, 3 moles of C are producedStep 3:Â  Find drateD/rateA c/coefficient of Ad coefficient of A x rateD/rateAd 2 x 0.025/0.050d 2 x 0.5d 1For every 2 moles of A, 1 mole of D is produced Answer The missing coefficients for the 2A bB → cC dD reaction are b6, c3, and d1.The balanced equation is 2A 6B → 3C D