Lithium nitrate, LiNO₃, decomposes on heating in a similar way to Group 2 nitrates to give the metal oxide, a brown gas and oxygen. Write an equation for the decomposition of LiNO₃.

1. (a)(i)Lithium nitrate, LiNO₃, decomposes on heating in a similar way to Group 2 nitrates to give the metal oxide, a brown gas and oxygen. Write an equation for the decomposition of LiNO₃.[1]
2. (a)(ii)The other Group 1 nitrates, MNO₃, decompose on heating to form the metal nitrite, MNO₂, and oxygen. The thermal stability of these nitrates increases down the group. Suggest why the thermal stability of MNO₃ increases down the group.[2]
3. (b)Acidified manganate(VII) ions, MnO₄⁻, can be used to analyse solutions containing nitrite ions, NO₂⁻, by titration. X is a solution of NaNO₂. 250.0 cm³ of X is added to 50.0 cm³ of 0.125 moldm⁻³ acidified MnO₄⁻(aq). The MnO₄⁻(aq) ions are in excess; all the NO₂⁻ ions are oxidised in the reaction. The unreacted MnO₄⁻(aq) required 22.50cm³ of 0.0400 moldm⁻³ Fe²⁺(aq) to reach the end-point. The relevant half-equations are shown. NO₂⁻ + H₂O ⇌ NO₃⁻ + 2H⁺ + 2e⁻ MnO₄⁻ + 8H⁺ + 5e⁻ ⇌ Mn²⁺ + 4H₂O Fe²⁺ ⇌ Fe³⁺ + e⁻ Calculate the concentration, in moldm⁻³, of NaNO₂ in X. concentration of NaNO₂ in X = ................................... moldm⁻³ [3][3]
4. (c)(i)Table 2.1 shows electrode potentials for some electrode reactions involving manganese compounds. Table 2.1 electrode reaction E°/V Mn²⁺ + 2e⁻ ⇌ Mn -1.18 MnO₂ + 4H⁺ + 2e⁻ ⇌ Mn²⁺ + 2H₂O +1.23 MnO₄⁻ + e⁻ ⇌ MnO₄²⁻ +0.56 MnO₄⁻ + 4H⁺ + 3e⁻ ⇌ MnO₂ + 2H₂O +1.67 MnO₄⁻ + 8H⁺ + 5e⁻ ⇌ Mn²⁺ + 4H₂O +1.52 MnO₄⁻ + 2H₂O + 3e⁻ ⇌ MnO₂ + 4OH⁻ +0.59 MnO₄²⁻ + 2H₂O + 2e⁻ ⇌ MnO₂ + 4OH⁻ +0.60 MnO₄²⁻ + 4H⁺ + 2e⁻ ⇌ MnO₂ + 2H₂O +1.70 Aqueous manganate(VI) ions, MnO₄²⁻, are unstable in acidic conditions and undergo a disproportionation reaction. The Ecell for this reaction is +1.14V. Construct an overall ionic equation for this disproportionation reaction.[2]
5. (c)(ii)Suggest and explain how the Ecell value of the disproportionation reaction changes with an increase in pH.[1]