Acid–base neutralization reactions Transitional Reasoning Practice

Questions

1. 1.

   A biomedical materials laboratory synthesizes calcium phosphate, $\text{Ca}_3(\text{PO}_4)_2$, for synthetic bone grafts via an acid–base neutralization reaction. In a controlled batch, exactly 19.6 g of pure phosphoric acid ($\text{H}_3\text{PO}_4$) in aqueous solution reacts completely with an adequate quantity of calcium hydroxide ($\text{Ca(OH)}_2$) according to the balanced equation: $$2\text{H}_3\text{PO}_4(\text{aq}) + 3\text{Ca(OH)}_2(\text{aq}) \rightarrow \text{Ca}_3(\text{PO}_4)_2(\text{s}) + 6\text{H}_2\text{O}(\text{l})$$ Assuming complete reaction, what mass of calcium phosphate precipitate is obtained? (Molar masses: $\text{H} = 1.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$, $\text{P} = 31.0\text{ g/mol}$, $\text{Ca} = 40.0\text{ g/mol}$)

   • A) 15.5 g
   • B) 31.0 g
   • C) 62.0 g
   • D) 93.0 g
2. 2.

   A pharmaceutical quality-control chemist tests a 3.90 g antacid tablet containing aluminum hydroxide, $\text{Al(OH)}_3$, and an inert binder. Complete neutralization of the $\text{Al(OH)}_3$ in the tablet requires exactly 0.090 mol of hydrochloric acid according to the reaction $\text{Al(OH)}_3 + 3\text{HCl} \rightarrow \text{AlCl}_3 + 3\text{H}_2\text{O}$. What is the percentage by mass of $\text{Al(OH)}_3$ in the antacid tablet? (Molar masses: $\text{Al} = 27.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$, $\text{H} = 1.0\text{ g/mol}$)

   • A) 20.0%
   • B) 40.0%
   • C) 90.0%
   • D) 60.0%
3. 3.

   A laboratory technician treats an acidic spill containing 0.60 mol of hydrochloric acid ($\text{HCl}$) by adding 23.2 g of solid magnesium hydroxide ($\text{Mg(OH)}_2$). Based on the balanced reaction $\text{Mg(OH)}_2 + 2\text{HCl} \rightarrow \text{MgCl}_2 + 2\text{H}_2\text{O}$, which substance is the limiting reactant, and what amount in moles of the excess reactant remains unreacted? (Molar mass of $\text{Mg(OH)}_2 = 58\text{ g/mol}$)

   • A) $\text{HCl}$ is limiting, and 0.10 mol of $\text{Mg(OH)}_2$ remains unreacted.
   • B) $\text{Mg(OH)}_2$ is limiting, and 0.20 mol of $\text{HCl}$ remains unreacted.
   • C) $\text{HCl}$ is limiting, and 0.20 mol of $\text{Mg(OH)}_2$ remains unreacted.
   • D) $\text{Mg(OH)}_2$ is limiting, and 0.10 mol of $\text{HCl}$ remains unreacted.
4. 4.

   An environmental chemist analyzes two acidic wastewater streams, Sample X containing nitric acid ($\text{HNO}_3$) and Sample Y containing sulfuric acid ($\text{H}_2\text{SO}_4$). Titration tests show that complete neutralization of a 250 mL portion of Sample X requires 0.20 mol of $\text{KOH}$, whereas complete neutralization of a 250 mL portion of Sample Y requires 0.30 mol of $\text{KOH}$. If both 250 mL portions are combined into a single vessel and neutralized using solid calcium hydroxide, $\text{Ca(OH)}_2$, instead of $\text{KOH}$, what mass of $\text{Ca(OH)}_2$ is required to achieve complete neutralization? (Molar mass of $\text{Ca(OH)}_2 = 74\text{ g/mol}$)

   • A) 37.0 g
   • B) 18.5 g
   • C) 9.25 g
   • D) 74.0 g
5. 5.

   A chemistry student prepares an aqueous solution containing 0.150 mol of sulfuric acid ($\text{H}_2\text{SO}_4$) and attempts to neutralize it completely by adding solid sodium hydroxide ($\text{NaOH}$). After dissolving 8.00 g of $\text{NaOH}$, testing with an indicator reveals that the solution remains acidic. According to the neutralization equation $\text{H}_2\text{SO}_4 + 2\text{NaOH} \rightarrow \text{Na}_2\text{SO}_4 + 2\text{H}_2\text{O}$, what additional mass of $\text{NaOH}$ must be added to achieve complete neutralization? (Molar masses: $\text{Na} = 23\text{ g/mol}$, $\text{O} = 16\text{ g/mol}$, $\text{H} = 1\text{ g/mol}$)

   • A) 2.00 g
   • B) 6.00 g
   • C) 4.00 g
   • D) 8.00 g

Answers and step-by-step solutions appear after you finish the test.