Practice Test 11

A student mixes two solutions in a sealed jar. Reaction: $$\mathrm{AgNO_3(aq) + NaCl(aq) \rightarrow AgCl(s) + NaNO_3(aq)}$$. Masses of reactant solutions added:

• $$\mathrm{AgNO_3}$$ solution: 40 g
• $$\mathrm{NaCl}$$ solution: 40 g The jar is sealed before mixing and remains sealed. After the precipitate forms, which total product mass is expected (not including the jar)?

A student performs the same gas-producing reaction two ways: Reaction: X(aq) + Y(aq) → Z(aq) + CO$_2$(g)

• Trial 1 (open cup): total mass before = 150 g; total mass after = 146 g
• Trial 2 (sealed flask): total mass before = 150 g; total mass after = 150 g Which statement best explains the different results?