Cl₂(g) + H₂O(l) ⇌ Cl⁻(aq) + ClO⁻(aq) + 2H⁺(aq) The addition of which of the following substances would move the above equilibrium to the right? A - Scottish Highers Chemistry - Question 15 - 2018

To determine which substance would shift the equilibrium to the right, we can use Le Chatelier's principle, which states that if an external change is applied to a system at equilibrium, the system will adjust to counteract that change.

1. Adding Hydrogen (A): This would not shift the equilibrium because there is no direct relation of hydrogen to the products.

2. Adding Hydrogen Chloride (B): This would also not contribute significantly as it does not enhance the formation of the products.

3. Adding Sodium Chloride (C): Adding sodium chloride introduces more chloride ions into the solution, but it does not change the equilibrium towards the products directly.

4. Adding Sodium Hydroxide (D): Sodium hydroxide reacts with the hydrogen ions (H⁺) and reduces their concentration. According to Le Chatelier's principle, this will result in a shift toward the right to produce more H⁺ ions, thus driving the reaction forward.

Based on the analysis, the correct answer is D. Sodium hydroxide.