10. Group 2
A section of Chemistry, 9701
Listing 10 of 275 questions
State how the solubilities of the hydroxides of the Group2 elements vary down the group. Explain the factors that are responsible for this variation. The solubility of Sr(OH)2 is 3.37×10–2 mol dm–3 at 0 °C. Write an expression for the solubility product of Sr(OH)2. Ksp =  Calculate the value of Ksp at 0 °C. Include units in your answer.  Ksp = units =  Metal peroxides contain the –O–O– ion. The peroxides of the Group2 elements, MO2, decompose on heating to produce a single gas and the solid oxide, MO, only. Write an equation for the thermal decomposition of strontiumperoxide, SrO2. Suggest how the temperature at which thermal decomposition of MO2 occurs varies down Group2. Explain your answer. The ethanedioates of the Group2 elements, MC2O4, decompose on heating to produce a mixture of two different gases and the solid oxide, MO, only. Complete the equation for the thermal decomposition of bariumethanedioate. BaC2O4 + +  Describe two observations you would make during the reaction when ethanedioicacid, H2C2O4, is warmed with acidified manganate(ions. 
9701_m18_qp_42
THEORY
2018
Paper 4, Variant 2
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The following table lists the solubilities of the hydroxides and carbonates of some of the Group2 elements, M, at 25 °C. element M solubility / mol dm–3 M(OH)2 MCO3 Mg 2.0 × 10–4 1.5 × 10–3 Ca 1.5 × 10–2 1.3 × 10–4 Sr 3.4 × 10–2 7.4 × 10–5 Ba 1.5 × 10–1 9.1 × 10–5 Explain why the solubility of the Group2 hydroxides, M(OH)2, increases down the group. Suggest a reason for the general decrease in the solubility of the Group 2 carbonates, MCO3, down the group. When carbon dioxide is passed through a saturated solution of calcium hydroxide , a white precipitate of calcium carbonate is formed. Use the data in the table to deduce, for each of Mg, Sr and Ba, whether or not a saturated solution of its hydroxide could also be used to test for carbon dioxide. Explain your answer. No calculations are required. Calculate the value of the solubility product, Ksp, of magnesium hydroxide at 25 °C.  Ksp =  State what would be observed if a few drops of a saturated solution of barium hydroxide are added to a saturated solution of barium carbonate. Explain your answer. observation explanation  The equation for the formation of the gaseous hydroxide ion is shown. 2H2+ 1 2O2+ e– OH–ΔH = (OH–) Use data in the table and from the Data Booklet to calculate (OH–). You might find it useful to construct a Born-Haber cycle. enthalpy change ΔH o / kJ mol–1 atomisation of Mg+148 formation of Mg(OH)2–925 lattice energy of Mg(OH)2–2993  (OH–) = kJ mol–1  
9701_m19_qp_42
THEORY
2019
Paper 4, Variant 2
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Group2 metals form stable carbonates and sulfates. State and explain the trend in the thermal stability of the Group2 carbonates down the group. The sulfates of Group2 elements become less soluble down the group. Explain this trend. Aluminium is extracted from Al 2O3 by electrolysis. Al 2O3 is dissolved in cryolite in this process. The half-equation for the reaction at the anode is shown. O2– + C → CO + 2e– Use this half-equation to write the ionic equation for the electrolysis of Al 2O3. Aluminiumoxide is electrolysed for 3.0hours using carbon electrodes and a current of 3.5×105A. Calculate the mass of aluminium that is formed.  mass of aluminium = g Cryolite can be made from SiF4. The first step in this conversion is the reaction of SiF4 with H2O, forming H2SiF6 and SiO2. Write an equation for this reaction. 
9701_m20_qp_42
THEORY
2020
Paper 4, Variant 2
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