Zinc reacts with hydrochloric acid according to the equation:

$\text{Zn}_{(s)} + 2\text{HCl}_{(aq)} \to \text{ZnCl}_{2(aq)} + \text{H}_{2(g)}$

A student reacts $0.650\ \text{g}$ of zinc with excess hydrochloric acid. The molar volume of a gas at STP is $22.7\ \text{dm}^3\ \text{mol}^{-1}$.

Sulfuric acid is titrated with sodium hydroxide solution.

$\text{H}_2\text{SO}_{4(aq)} + 2\text{NaOH}_{(aq)} \to \text{Na}_2\text{SO}_{4(aq)} + 2\text{H}_2\text{O}_{(l)}$

A $25.00\ \text{cm}^3$ sample of sulfuric acid is exactly neutralized by $23.60\ \text{cm}^3$ of $0.1000\ \text{mol dm}^{-3}$ sodium hydroxide.

Calcium carbonate is precipitated when calcium chloride solution reacts with sodium carbonate solution.

$\text{CaCl}_{2(aq)} + \text{Na}_2\text{CO}_{3(aq)} \to \text{CaCO}_{3(s)} + 2\text{NaCl}_{(aq)}$

A $25.0\ \text{cm}^3$ sample of $0.200\ \text{mol dm}^{-3}$ calcium chloride is reacted with excess sodium carbonate. The dry mass of calcium carbonate collected is $0.478\ \text{g}$.

A gaseous hydrocarbon is burned completely in oxygen. The stimulus shows the formula of the hydrocarbon and gas-volume data collected at the same temperature and pressure.

A student determined the concentration of sulfuric acid by titration with sodium hydroxide. The stimulus shows the equation and titration data.

Calcium carbonate was heated strongly until no further visible change occurred. The stimulus shows the decomposition equation and mass data for the solid product.

Aluminium reacts with iron(III) oxide in the thermite reaction.

$2\text{Al}_{(s)} + \text{Fe}_2\text{O}_{3(s)} \to \text{Al}_2\text{O}_{3(s)} + 2\text{Fe}_{(l)}$

A mixture contains $4.00\ \text{g}$ of aluminium and $12.0\ \text{g}$ of iron(III) oxide.

Ethanol can be produced by different reactions.

Reaction 1: $\text{C}_2\text{H}_4 + \text{H}_2\text{O} \to \text{C}_2\text{H}_5\text{OH}$

Reaction 2: $\text{C}_2\text{H}_5\text{Br} + \text{NaOH} \to \text{C}_2\text{H}_5\text{OH} + \text{NaBr}$

Ethanol is the desired product in both reactions.

Nitrogen and hydrogen react to form ammonia.

$\text{N}_{2(g)} + 3\text{H}_{2(g)} \to 2\text{NH}_{3(g)}$

$12.0\ \text{dm}^3$ of nitrogen is mixed with $30.0\ \text{dm}^3$ of hydrogen at the same temperature and pressure.

A sample of hydrated copper(II) sulfate, $\text{CuSO}_4 \cdot x\text{H}_2\text{O}$, has a mass of $2.495\ \text{g}$. It is heated to constant mass, leaving $1.596\ \text{g}$ of anhydrous $\text{CuSO}_4$.

Two routes for preparing ethanoic acid are shown.

Route A: $\text{CH}_3\text{OH} + \text{CO} \to \text{CH}_3\text{COOH}$

Route B: $\text{C}_2\text{H}_5\text{OH} + \text{O}_2 \to \text{CH}_3\text{COOH} + \text{H}_2\text{O}$

Ethanoic acid is the desired product.

A precipitate of silver chloride is formed by mixing aqueous silver nitrate with aqueous sodium chloride. The stimulus shows the balanced equation and experimental data.

Magnesium reacts with excess hydrochloric acid to form hydrogen gas. The graph shows the volume of hydrogen collected against time. The molar volume of gas under the laboratory conditions is given in the stimulus.

Hydrogen can be produced by different reactions. The stimulus compares two reactions where hydrogen is the desired product.

Aqueous silver nitrate is mixed with aqueous sodium chloride.

$\text{AgNO}_{3(aq)} + \text{NaCl}_{(aq)} \to \text{AgCl}_{(s)} + \text{NaNO}_{3(aq)}$

$35.0\ \text{cm}^3$ of $0.120\ \text{mol dm}^{-3}$ silver nitrate is mixed with $50.0\ \text{cm}^3$ of $0.0750\ \text{mol dm}^{-3}$ sodium chloride.

An impure sample of sodium carbonate is analysed by titration.

$\text{Na}_2\text{CO}_{3(aq)} + 2\text{HCl}_{(aq)} \to 2\text{NaCl}_{(aq)} + \text{H}_2\text{O}_{(l)} + \text{CO}_{2(g)}$

A $0.212\ \text{g}$ sample requires $32.40\ \text{cm}^3$ of $0.1000\ \text{mol dm}^{-3}$ hydrochloric acid for complete reaction.

An impure sample of sodium hydrogencarbonate reacts with excess hydrochloric acid.

$\text{NaHCO}_{3(s)} + \text{HCl}_{(aq)} \to \text{NaCl}_{(aq)} + \text{H}_2\text{O}_{(l)} + \text{CO}_{2(g)}$

A $1.20\ \text{g}$ sample produces $0.285\ \text{dm}^3$ of carbon dioxide at STP. The molar volume of a gas at STP is $22.7\ \text{dm}^3\ \text{mol}^{-1}$.

An antacid tablet containing calcium carbonate was analysed by back titration. The tablet was reacted with excess hydrochloric acid, and the remaining acid was titrated with sodium hydroxide. The stimulus shows the relevant equations and data.

Aspirin can be prepared by reacting salicylic acid with ethanoic anhydride. The stimulus shows the equation, reagent data and melting range data for crude and recrystallized product.

Two processes for producing ethene oxide, $C_2H_4O$, are compared in the stimulus. Ethene oxide is the desired product.

Aqueous barium hydroxide and hydrochloric acid were mixed. The reaction was assumed to go to completion and volumes were treated as additive. The stimulus shows an initial-change-final table with some entries omitted.

A sample of impure calcium carbonate was analysed by adding excess hydrochloric acid. The calcium carbonate reacts according to the equation:

$CaCO_3(s) + 2HCl(aq) \to CaCl_2(aq) + CO_2(g) + H_2O(l)$

A $2.50\ \text{g}$ sample was added to $100.0\ \text{cm}^3$ of $0.250\ \text{mol dm}^{-3}$ hydrochloric acid. The acid remaining after reaction required $18.60\ \text{cm}^3$ of $0.100\ \text{mol dm}^{-3}$ sodium hydroxide for neutralisation.

Nitrogen and hydrogen react to form ammonia according to the equation:

$N_2(g) + 3H_2(g) \to 2NH_3(g)$

A mixture contains $4.50\ \text{dm}^3$ of nitrogen and $10.0\ \text{dm}^3$ of hydrogen at the same temperature and pressure.

Ethanol can be manufactured by different processes.

Process 1: $C_2H_4(g) + H_2O(g) \to C_2H_5OH(g)$

Process 2: $C_6H_{12}O_6(aq) \to 2C_2H_5OH(aq) + 2CO_2(g)$

In each process, ethanol is the desired product.

A gaseous mixture of methane and ethane was completely burned in oxygen. All gas volumes were measured at the same temperature and pressure after water vapour had condensed. The stimulus shows gas-volume data.

Sodium hydrogencarbonate decomposes on heating. Repeated heating mass data are shown in the stimulus.

Aqueous barium chloride and aqueous sodium sulfate are mixed to produce a precipitate of barium sulfate. A student mixes $25.0\ \text{cm}^3$ of $0.200\ \text{mol dm}^{-3}$ barium chloride with $40.0\ \text{cm}^3$ of $0.150\ \text{mol dm}^{-3}$ sodium sulfate.

Ethanol undergoes complete combustion in oxygen to form carbon dioxide and water. A sample contains $2.30\ \text{g}$ ethanol, $C_2H_5OH$. In a second combustion, $3.00\ \text{dm}^3$ of oxygen is supplied at the same conditions. The molar volume of a gas at the stated conditions is $22.7\ \text{dm}^3\ \text{mol}^{-1}$.

A student determines the concentration of sulfuric acid by titration with sodium hydroxide.

$H_2SO_4(aq) + 2NaOH(aq) \to Na_2SO_4(aq) + 2H_2O(l)$

A $20.00\ \text{cm}^3$ sample of sulfuric acid requires $24.60\ \text{cm}^3$ of $0.0950\ \text{mol dm}^{-3}$ sodium hydroxide for complete neutralisation.

Aspirin, $C_9H_8O_4$, can be prepared by reacting salicylic acid, $C_7H_6O_3$, with ethanoic anhydride, $C_4H_6O_3$:

$C_7H_6O_3(s) + C_4H_6O_3(l) \to C_9H_8O_4(s) + C_2H_4O_2(l)$

A student reacts $2.00\ \text{g}$ salicylic acid with $5.00\ \text{cm}^3$ ethanoic anhydride. The density of ethanoic anhydride is $1.08\ \text{g cm}^{-3}$. The student obtains $2.18\ \text{g}$ aspirin after purification.

Sulfur dioxide and oxygen react to form sulfur trioxide in the Contact process:

$2SO_2(g) + O_2(g) \to 2SO_3(g)$

A reactor is charged with $150\ \text{dm}^3$ sulfur dioxide and $90.0\ \text{dm}^3$ oxygen at the same temperature and pressure. The gases behave ideally for the purpose of this stoichiometric calculation. For part (b), the actual yield of sulfur trioxide is $85.0\%$ of the theoretical yield.

Phosphate ions can be removed from wastewater by precipitation with aluminium ions:

$Al^{3+}(aq) + PO_4^{3-}(aq) \to AlPO_4(s)$

A treatment trial mixes $250.0\ \text{cm}^3$ of $0.0180\ \text{mol dm}^{-3}$ aluminium sulfate, $Al_2(SO_4)_3(aq)$, with $500.0\ \text{cm}^3$ of $0.0120\ \text{mol dm}^{-3}$ sodium phosphate, $Na_3PO_4(aq)$.