15. The function of the acid-base indicator, In, can be expressed using the equation below
In+H2O ⇋InH^+ OH^−; Kc=35
Blue Yellow
Which of the below statements are correct?
I. The solution becomes darker blue with the addition of an acid
II. The solution is a pale green at equilibrium
III. Kc increases with the addition of an alkali
B
Explanation:
Kc>1, and so lies towards the right with the yellow product at equilibrium; the color would therefore be a pale green due to more yellow than blue.
When an acid is added, it reacts with the OH−reducing its concentration. Equilibrium shifts to the right to oppose that change.
Kc only changes with temperature. Adding an alkali would increase the OH− concentration and therefore the equilibrium would shift to the left to oppose that change. Kc again would remain the same as it is only affected by temperature.