Le Chatelier's Principle in Precipitation Equilibrium

Steps:

• The equilibrium is BiCl3(aq) + H2O(l) ⇌ BiOCl(s) + 2HCl(aq); increasing BiOCl shifts right.
• Adding more water increases reactant concentration and dilutes products, shifting equilibrium right to form more BiOCl precipitate.
• Adding aqueous NaOH neutralizes HCl (H+ + OH- → H2O), removing a product and shifting equilibrium right to produce more BiOCl.
• Adding dilute HCl increases product concentration, shifting equilibrium left and decreasing BiOCl precipitate.

Why A is correct:

• Both adding water (dilutes products) and NaOH (removes HCl product) drive the equilibrium right per Le Chatelier's principle, increasing BiOCl mass.

Why the others are wrong:

• B includes adding HCl, which increases products and shifts left, reducing precipitate.
• C ignores NaOH's effect in removing HCl to shift right.
• D pairs NaOH (shifts right) with HCl (shifts left), so not both increase precipitate.

Final answer: A