Which of the following gives a precipitate when treated with NaOH solution?

When a substance reacts with NaOH solution to produce a solid or insoluble product, it is said to give a precipitate. We can use this knowledge to determine which of the given options will give a precipitate when treated with NaOH solution. Option A, AlCl3, will give a precipitate when treated with NaOH solution. This is because AlCl3 is an acidic salt and will react with the basic NaOH to produce a gelatinous precipitate of aluminium hydroxide (Al(OH)3), which is insoluble in water. Option B, NH4Cl, will not give a precipitate when treated with NaOH solution because NH4Cl is a salt of a strong acid (HCl) and a weak base (NH3), and it will not react with NaOH to form a precipitate. Option C, CH3COONa, will not give a precipitate when treated with NaOH solution because it is a salt of a weak acid (acetic acid) and a strong base (NaOH). Therefore, it will not react with NaOH to form a precipitate. Option D, Na2CO3, will give a precipitate when treated with NaOH solution. This is because Na2CO3 is a basic salt and will react with the acidic NaOH to produce a white precipitate of sodium carbonate (Na2CO3), which is insoluble in water. Therefore, the option that gives a precipitate when treated with NaOH solution is option A, AlCl3, and option D, Na2CO3. The answer is not uniquely defined.