At T(K), for the reaction:
H2(g) + I2(g) → 2HI(g), \( \displaystyle\frac{\Delta[\text{HI}]}{\Delta t} \)
is found to be 2 × 10−4 mol L−1 min−1. What is the average rate of this reaction in mol L−1 min−1?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 10−4
For a reaction, the rate is the rate of change of concentration of any species divided by its stoichiometric coefficient, so that it has one value for the whole reaction. For H2(g) + I2(g) → 2HI(g):
\( \displaystyle \text{Rate} = -\frac{\Delta[\ce{H2}]}{\Delta t} = -\frac{\Delta[\ce{I2}]}{\Delta t} = \frac{1}{2}\frac{\Delta[\ce{HI}]}{\Delta t} \)
\( \displaystyle \text{Rate} = \frac{1}{2} \times 2 \times 10^{-4} = 1 \times 10^{-4}\ \text{mol L}^{-1}\,\text{min}^{-1} \)