Question

In a reaction $2HI \to H_{2} + I_{2}$, the concentration of $HI$ decreases from $0.5\, mol\, L^{-1}$ to $0.4 \,mol \,L^{-1}$ in $10$ minutes. What is the rate of reaction during this interval?

• A. $5 \times 10^{-3} M\, min^{-1}$
• B. $2.5 \times 10^{-3} M \, min^{- 1}$
• C. $5 \times 10^{-2} M\, min^{-1}$
• D. $2.5 \times 10^{-2} M \,min^{-1}$

Answer 1

Answer: (A)

Average rate $=-\frac{1}{2} \frac{\Delta[R]}{\Delta t}=-\frac{1}{2}\times\frac{0.4-0.5}{10}$
$=\frac{1}{2}\times\frac{0.1}{10}=5\times10^{-3} M min^{-1}$