Acids, Bases and Salts

Calcium oxide and magnesium sulfide each react with acid.

CaO(s) + 2H⁺(aq) → Ca²⁺(aq) + H₂O(l)
MgS(s) + 2H⁺(aq) → Mg²⁺(aq) + H₂S(g)

A mixture of these two compounds, X, reacts with exactly 0.125 mol of dilute hydrochloric acid. The amount of hydrogen sulfide formed is 0.0250 mol. What is the mass of calcium oxide in mixture X?

The mineral dolomite is a double carbonate of magnesium and calcium, CaMg(CO₃)₂. When 2.00 g of an impure sample of dolomite was completely dissolved in excess hydrochloric acid, 0.45 g of carbon dioxide was given off. CaMg(CO₃)₂ + 4HCl → MgCl₂ + CaCl₂ + 2CO₂ + 2H₂O. What is the percentage purity of the sample?

Excess magnesium powder is added to 25 cm³ of 0.10 mol/dm³ solutions of three different acids: (1) methanoic acid, HCOOH, a weak monobasic acid, (2) hydrochloric acid and (3) sulfuric acid. Which statement is correct?

The table shows the results of experiments on two acids, K and L, of equal concentration.

Which deduction can be made about the two acids?

All ammonium salts produce ammonia gas when heated with sodium hydroxide. From which ammonium salt can the greatest mass of ammonia be obtained?

A sodium nitrate solution is prepared by adding 0.10 mol of sodium nitrate, NaNO₃, to 2.00 L of water. Which of the following is incorrect?

Which of the following has the lowest pH?

Rainfall from unpolluted air should be

To obtain the magnesium compound in a mineral ore containing impurities of Al₂O₃ and P₄O₁₀, which reagent could be used to dissolve the impurities in the ore?

Which pair is not a Brønsted–Lowry conjugate acid–base pair?

Which statement about the ammonium ion, NH₄⁺, is incorrect?

In which reactions does NH₃ behave as a Lewis base?

1 2NH₃ → NH₂⁻ + NH₄⁺
2 HSO₄⁻ + NH₃ → SO₄²⁻ + NH₄⁺
3 Ag⁺ + 2NH₃ → [Ag(NH₃)₂]⁺

The following reaction takes place in a suitable solvent: Na⁺NH₂⁻ + NH₄⁺Cl⁻ → Na⁺Cl⁻ + 2NH₃. Which statements explain why this is a Brønsted–Lowry acid–base reaction?

1 NH₂⁻ is an electron pair acceptor.
2 NH₂⁻ and NH₃ are a conjugate acid–base pair.
3 The ammonium ion acts as a proton donor.

BF₃ reacts with (CH₃)₃N to give (CH₃)₃NBF₃. Which statement is correct?

Ammonium carbonate is a crystalline solid. On gentle warming a reaction occurs, forming ammonia as one product. How are the carbonate ions behaving during this reaction?

A sample of solid magnesium hydroxide is prepared by adding an excess of aqueous sodium hydroxide to an aqueous solution containing 1.20 g of magnesium sulfate. The mass of magnesium hydroxide collected is 0.32 g. What is the percentage yield?

10.0 cm³ of 0.10 mol/dm³ lead(II) nitrate, Pb(NO₃)₂, is added to 30.0 cm³ of 0.05 mol/dm³ sodium chloride, NaCl. After the reaction a white precipitate of lead(II) chloride is present. What else is present?

Leo accidentally contaminated a sample of pure lead(II) sulfate with a small amount of lead(II) carbonate. Which sequence of steps would help Leo re-obtain pure lead(II) sulfate?

20 cm³ of an aqueous 1.0 mol/dm³ solution of the hydroxide of metal X exactly neutralises 40 cm³ of 0.25 mol/dm³ dilute sulfuric acid. What is the formula of the sulfate of X?

A sample of lithium oxide, Li₂O, is dissolved in 250 cm³ of distilled water. 25.0 cm³ of the solution is neutralised by 30.0 cm³ of 0.5 mol/dm³ dilute sulfuric acid. What is the mass of lithium oxide dissolved in the 250 cm³ of water?

Dilute sulfuric acid, dilute nitric acid and dilute ethanoic acid were separately titrated with 0.10 mol/dm³ aqueous sodium hydroxide. The same volume and concentration of each acid was used. In order to react completely,

A tablet of aspirin, C₉H₈O₄, is crushed and dissolved in water. The acid in the tablet is neutralised by 12.25 cm³ of 0.147 mol/dm³ sodium hydroxide: C₉H₈O₄ + NaOH → C₉H₇O₄Na + H₂O. One grain of aspirin is 0.0648 g. How many grains of aspirin are there in the tablet? [M_r: C₉H₈O₄ 180]

Oxalic acid, H₂C₂O₄, is a dibasic acid. 25.0 cm³ of oxalic acid solution reacts completely with 15.0 cm³ of 2.50 mol/dm³ aqueous sodium hydroxide. What is the concentration of the oxalic acid?

Group 1 and Group 2 ionic hydrides react with water: H⁻ + H₂O → OH⁻ + H₂. In an experiment, 1.01 g of a sample of an ionic hydride is dissolved in excess water. The resulting solution required 24.0 cm³ of 2.0 mol dm⁻³ HCl for complete neutralisation. What is the formula of the hydride?

The salt (C₂H₅)₄N⁺Cl⁻ is reacted with hydrogen chloride to form a white solid X, which is dissolved in water to form an acidic solution. 20 cm³ of this solution required 24.6 cm³ of 0.1 M NaOH for neutralisation. Another 20 cm³ of the same solution needed exactly 49.2 cm³ of 0.1 M aqueous AgNO₃ for complete precipitation of AgCl. What is the anion in solid X?