Concept:

Bismuth oxychloride (\( \text{BiOCl} \)) is highly insoluble in water and forms a thick, cloudy white precipitate. To clear the solution, the equilibrium must be forced backward to dissolve the solid.

Formula:

$$ \text{BiCl}_{3(aq)} + \text{H}_2\text{O}_{(l)} \rightleftharpoons \text{BiOCl}_{(s)} \text{ [Cloudy]} + 2\text{HCl}_{(aq)} $$

Solution:

• The cloudiness is entirely due to the presence of the product, solid \( \text{BiOCl} \).



• To make the solution clear, we must push the equilibrium to the left (towards the fully soluble \( \text{BiCl}_3 \) reactants).



• According to Le Chatelier's Principle, adding an excess of a product forces the reaction backward.



• Therefore, adding concentrated \( \text{HCl} \) increases product concentration, forcing the solid \( \text{BiOCl} \) to react and dissolve back into clear \( \text{BiCl}_3 \).

Why other options are incorrect:

Adding \( \text{BiCl}_3 \) or \( \text{H}_2\text{O} \) (reactants) shifts the reaction forward, making it even cloudier. Adding \( \text{BiOCl} \) directly adds more cloudy precipitate.