[Four-digit Integer] The equilibrium: p-xyloquinone + methylene white ⇌ p-xylohydroquinone + methyle — Chemical Equilibrium Chemistry Question
Question
[Four-digit Integer] The equilibrium: p-xyloquinone + methylene white ⇌ p-xylohydroquinone + methylene blue may be studied by observing colour difference. One millimole of methylene blue was added to 1.00 L of solution 0.24 M in p-xylohydroquinone and 0.012 M in p-xyloquinone. 4.0% of the added methylene blue was reduced to methylene white. What is the equilibrium constant?
💡 Solution & Explanation
The equilibrium: p-xyloquinone (Q) + methylene white (W) $\rightleftharpoons$ p-xylohydroquinone (QH$_2$) + methylene blue (B) \[ K_c = \frac{[\text{QH}_2][\text{B}]}{[\text{Q}][\text{W}]} \] Given data (reading from optical measurements): \begin{align*} [\text{W}]_{\text{eq}} &= 4\times10^{-5}\ \text{M} \\ [\text{B}]_{\text{eq}} &= 9.6\times10^{-4}\ \text{M} \\ [\text{Q}]_{\text{eq}} &= 0.012\ \text{M} \\ [\text{QH}_2]_{\text{eq}} &= 0.24\ \text{M} \end{align*} \[ K_c = \frac{0.24 \times 9.6\times10^{-4}}{0.012 \times 4\times10^{-5}} = \frac{2.304\times10^{-4}}{4.8\times10^{-7}} = 480 \] \textbf{Answer: 0480}