Questions: Part A Which of the following solutions will not form a precipitate when added to 0.10 M NaOH ? 0.10 M FeCl2 0.10 M NH4Br 0.10 M MgBr2

Solution Steps

When a solution is added to 0.10 M NaOH, we need to consider the possible reactions that could occur, specifically the formation of insoluble hydroxides. The relevant reactions are:

1. \( \text{FeCl}_2 + 2\text{NaOH} \rightarrow \text{Fe(OH)}_2 \downarrow + 2\text{NaCl} \)
2. \( \text{NH}_4\text{Br} + \text{NaOH} \rightarrow \text{NH}_3 \uparrow + \text{H}_2\text{O} + \text{NaBr} \)
3. \( \text{MgBr}_2 + 2\text{NaOH} \rightarrow \text{Mg(OH)}_2 \downarrow + 2\text{NaBr} \)

• Fe(OH)\(_2\): Iron(II) hydroxide is insoluble in water and will form a precipitate.
• NH\(_3\): Ammonia is a gas and will not form a precipitate.
• Mg(OH)\(_2\): Magnesium hydroxide is insoluble in water and will form a precipitate.

From the reactions and solubility information, we see that:

• \( \text{FeCl}_2 \) forms a precipitate of Fe(OH)\(_2\).
• \( \text{NH}_4\text{Br} \) does not form a precipitate; instead, it releases ammonia gas.
• \( \text{MgBr}_2 \) forms a precipitate of Mg(OH)\(_2\).

Final Answer