氧化還原與第1、2、7族元素：練習題

Which of the following describes the correct trend in the first ionisation energy of Group 2 elements as the atomic number increases?

Which of the following reactions shows chlorine acting as both an oxidising agent and a reducing agent?

A solution contains both \(\text{Ba}^{2+}\) and \(\text{Mg}^{2+}\) ions at a concentration of \(0.100 \text{ mol dm}^{-3}\). Aqueous sodium sulfate is added slowly to this solution. Which statement correctly describes the observations and the underlying reason?

What is the average oxidation number of sulfur in the tetrathionate ion, \( \text{S}_4\text{O}_6^{2-} \)?

Magnesium reacts very slowly with cold water but rapidly with steam. Which of the following is correct for the reaction of magnesium with steam?

Explain the trend in the thermal stability of Group 2 carbonates, \( \text{MCO}_3 \), as the group is descended from magnesium to barium.

Using the half-equation method, construct the full balanced ionic equation for the reaction between acidified manganate(VII) ions, \( \text{MnO}_4^{-} \), and iron(II) ions, \( \text{Fe}^{2+} \), to produce \( \text{Mn}^{2+} \) and \( \text{Fe}^{3+} \) ions.

A solution contains an unknown halide ion, \( \text{X}^- \). When acidified silver nitrate solution is added, a cream precipitate forms that is insoluble in dilute aqueous ammonia but dissolves in concentrated aqueous ammonia. Identify the halide ion and write the ionic equation for the formation of the precipitate, including state symbols.

The halogens in Group 7 show distinct trends in their physical properties and chemical reactivity.

(a) Explain the trend in the boiling temperatures of the halogens from fluorine to iodine in terms of intermolecular forces.

(b) Describe what is observed when an aqueous solution of chlorine is added to a solution of potassium bromide. Include an ionic equation for the reaction.

(c) Predict and explain the relative reactivity of astatine (\( \text{At} \)) compared to iodine (\( \text{I} \)) in displacement reactions.

A 3.183 g mixture contains anhydrous magnesium nitrate, \( \text{Mg(NO}_3)_2 \), and anhydrous sodium nitrate, \( \text{NaNO}_3 \). The mixture is heated strongly until it completely decomposes to form solid residues and a mixture of gases. The total volume of gas collected at room temperature and pressure (r.t.p.) is 840 cm³.

(a) Write balanced chemical equations for the thermal decomposition of both nitrates. Include state symbols.

(b) Calculate the percentage by mass of magnesium nitrate in the original mixture. (Assume the molar volume of gas at r.t.p. is \( 24,000 \text{ cm}^3 \text{ mol}^{-1} \). Relative atomic masses: \( \text{Na} = 23.0, \text{Mg} = 24.3, \text{N} = 14.0, \text{O} = 16.0 \))

(c) In terms of the properties of the metal cations, explain why sodium nitrate is more thermally stable than magnesium nitrate.

(d) The gases produced from the decomposition of magnesium nitrate are passed through an excess of cold, aqueous sodium hydroxide. Write the balanced ionic equation for the reaction that occurs between nitrogen dioxide and the hydroxide ions, and state the oxidation numbers of nitrogen in the products.