CIE Jun 2017 v2 Paper 4 Q1

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Answer all the questions in the spaces provided. PMT (a) (i) Describe and explain the variation in the thermal stabilities of the carbonates of the Group 2 elements.[3] (ii) Suggest and explain a reason why sodium carbonate is more stable to heat than magnesium carbonate.[1] (b) Sodium hydrogencarbonate, NaHCO3, and potassium hydrogencarbonate, KHCO3, decompose on heating to produce gases and the solid metal carbonate. (i) Write an equation for the decomposition of KHCO3.[1] (ii) Predict which of NaHCO3 or KHCO3 will decompose at the lower temperature. Explain your answer.[1]UCLES 2017 9701/42/M/J/17<br /> PMT (c) (i) Use the data in the table below, and relevant data from the Data Booklet, to calculate the lattice energy, , of potassium oxide, K2O(s). energy change value / kJ mol1 enthalpy change of atomisation of potassium, electron affinity of O(g) electron affinity of O(g) enthalpy change of formation of potassium oxide, K(s) K2O(s) +89 141 +798 361 =kJ mol1 [3] (ii) State whether the lattice energy of Na2O would be more negative, less negative or the same as that of K2O. Give reasons for your answer.[1]UCLES 2017 9701/42/M/J/17 [Total: 10] [Turn over<br />

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