10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
A subsection of Chemistry, 9701, through 10. Group 2
Listing 10 of 275 questions
State and explain the trend observed in the thermal stability of the Group2 nitrates. Lead(nitrate, Pb(NO3)2, decomposes on heating in a similar manner to the Group2 nitrates. Write an equation for the decomposition of lead(nitrate. Suggest how the ease of decomposition of Pb(NO3)2 would compare to that of Ba(NO3)2. Explain your answer. You may find it useful to refer to the Data Booklet. Bariumethanedioate, BaC2O4, decomposes on heating to produce bariumoxide and a mixture of two different gases. Construct an equation for the decomposition of barium ethanedioate. An impure sample of BaC2O4, of mass 0.500 g, is added to 50.0 cm3 of 0.0200 mol dm–3 acidified MnO4 –, an excess. A redox reaction takes place and all the BaC2O4 reacts. The resulting solution, containing unreacted acidified MnO4 –, is titrated with 0.0500 mol dm–3 Fe2+. The end-point is reached when 30.40 cm3 of 0.0500 mol dm–3 Fe2+has been added. C2O4 2– 2CO2 + 2e– MnO4 – + 8H+ + 5e– Mn2+ + 4H2O Fe2+ Fe3+ + e– Calculate the percentage by mass of BaC2O4 in the 0.500 g impure sample. Show your working. [Mr: BaC2O4, 225.3]  percentage by mass of BaC2O4 = Bariumhydroxide, Ba(OH)2, is completely dissociated in aqueous solution. Calculate the pH of 0.120 mol dm–3 Ba(OH)2at 298 K.  pH = 
9701_s21_qp_42
THEORY
2021
Paper 4, Variant 2
View
Calcium, magnesium and radium are Group2 elements. Radium follows the same trends as the other members of Group 2. Identify the highest energy orbital which contains electrons in a calcium atom. Sketch the shape of this orbital. identity of highest energy orbital in Ca shape  Write the equation for the thermal decomposition of calcium nitrate. Suggest which of the Group2 nitrates, calcium, magnesium or radium, requires the highest temperature to decompose. Explain your answer. Predict what you would observe when aqueous radium chloride is added to aqueous sodiumsulfate. Do not refer to temperature changes in your answer. 25Mg is an isotope of magnesium. Determine the number of protons and neutrons in an atom of 25Mg . number of protons number of neutrons  State the full electronic configuration of an atom of 25Mg . A sample of magnesium contains three isotopes, 25Mg, 26Mg and X. The percentage abundance of the three isotopes is shown in Table 1.1. Table 1.1 isotope of Mg mass / a.m.u. percentage abundance / % X 78.99 25Mg 24.99 10.00 26Mg 25.98 11.01 The relative atomic mass, Ar, is calculated by comparing the average mass of the isotopes of an element to the unified atomic mass unit. Define the unified atomic mass unit. Calculate the mass of X. Use data from Table 1.1 and Ar = 24.31 in your calculation. Show your working.  mass of X =  State one similarity and one difference in the properties of these isotopes of magnesium. Explain your answer. Magnesium, Mg, burns in oxygen, O2. The activation energy, Ea, for this reaction is +148 kJ mol–1. State one observation when magnesium burns in oxygen. Do not refer to temperature changes in your answer. On : ● sketch a reaction pathway diagram for the reaction that occurs when Mg burns in O2 ● label the diagram to show the enthalpy change, ∆H, and the activation energy, Ea, for the reaction. enthalpy progress of reaction  Cold water reacts slowly with a piece of Mg to produce bubbles of H2. Cold water reacts rapidly with burning Mg to produce H2in an explosive mixture. Mg + 2H2O Mg(OH)2 + H2 Explain why the rate of reaction of cold water with burning magnesium is greater. 
9701_s22_qp_21
THEORY
2022
Paper 2, Variant 1
View
The solubility of the Group2 sulfates decreases down the group. Explain this trend. Describe what is observed when magnesium and barium are reacted separately with an excess of dilute sulfuricacid. magnesium barium  The solubility product, Ksp, of BaSO4 is 1.08×10–10 mol2 dm–6 at 298 K. Calculate the solubility of BaSO4 in g per 100 cm3 of solution.  solubility of BaSO4 = g per 100 cm3 of solution  The equation for the formation of a gaseous sulfate ion is shown. S+ 2O2+ 2e– → SO4 2–∆H = of SO4 2–Calculate the standard enthalpy change of formation, , of SO4 2–. It may be helpful to draw a labelled energy cycle. Use relevant data from Table1.1 in your calculations. Table 1.1 energy change value / kJ mol–1 lattice energy of barium sulfate, BaSO4–2469 standard enthalpy change of formation of barium sulfate –1473 standard enthalpy change of atomisation of barium +180 first ionisation energy of barium +503 second ionisation energy of barium +965 standard enthalpy change of atomisation of sulfur +279 standard enthalpy change for S→ S2–+440 standard enthalpy change for O→ O2–+657 O=O bond energy +496  of SO4 2–= kJ mol–1 Suggest how the lattice energy of BaSO4differs from the lattice energy of Cs2SO4. Explain your answer. The reaction of solid hydrated barium hydroxide, Ba(OH)2•8H2O, with ammonium salts is endothermic. Calculate the minimum temperature at which the reaction of Ba(OH)2•8H2O with NH4NO3 becomes feasible. Show all your working. Ba(OH)2•8H2O+ 2NH4NO3→ 2NH3+ Ba(NO3)2+ 10H2O= +132 kJ mol–1 ∆S o = +616 J K–1 mol–1  temperature = °C Bariumhydroxide reacts readily with ammoniumchloride on mixing at room temperature. Ba(OH)2•8H2O+ 2NH4Cl → 2NH3+ BaCl 2•2H2O+ 8H2O = +133 kJ mol–1 Some relevant standard entropies are given in Table 1.2. Table 1.2 substance Ba(OH)2•8H2ONH4Cl NH3BaCl 2•2H2OH2OS o / J K–1 mol–1 Calculate the standard Gibbs free energy change, ∆G o, for this reaction at 25 °C. ∆G o = kJ mol–1 
9701_s22_qp_41
THEORY
2022
Paper 4, Variant 1
View
The solubility of the Group2 hydroxides increases down the group. Explain this trend. The solubility of Be(OH)2 in water is 2.40×10–6 g dm–3 at 298 K. Write an expression for the solubility product, Ksp, of Be(OH)2 and state its units. Ksp =  units =  Calculate the numerical value of Ksp for Be(OH)2 at 298 K.  Ksp = Be(OH)2 is soluble in aqueous solutions containing an excess of hydroxide ions and forms the complex ion [Be(OH)4]2–. This complex ion has a similar shape to that of [CuCl 4]2–. Define the term complex ion. Draw a three-dimensional diagram to show the structure of the complex ion [Be(OH)4]2–. Name the shape of the [Be(OH)4]2– complex ion. shape  Explain why transition elements can form complex ions. Complete Table1.1 to show the coordination number of each metal ion, and the shapes and overall polarities of the complex ions listed. Table 1.1 complex ion shape coordination number polar or non-polar cis-[Pt(H2NCH2CH2NH2)Cl 2] square planar [Ag(NH3)2]+ non-polar [Fe(C2O4)3]3–  Define stability constant, Kstab. Nickel can form complexes with the ligands en, H2NCH2CH2NH2, and tn, H2NCH2CH2CH2NH2, as shown. equilibrium1 [Ni(H2O)6]2+ + 3en 2+ + 6H2O Kstab = 6.76 × 1017 equilibrium2 [Ni(H2O)6]2+ + 3tn 2+ + 6H2O Kstab = 1.86 × 1012 Construct an expression for the stability constant, Kstab, for equilibrium1. State the units for Kstab. Kstab =  units =  Describe what the Kstab values indicate about the position of equilibrium for equilibrium1 and 2. Use the Kstab values to deduce which complex, 2+ or 2+, is more stable. 
9701_s22_qp_42
THEORY
2022
Paper 4, Variant 2
View
The solubility of the Group2 sulfates decreases down the group. Explain this trend. Describe what is observed when magnesium and barium are reacted separately with an excess of dilute sulfuricacid. magnesium barium  The solubility product, Ksp, of BaSO4 is 1.08×10–10 mol2 dm–6 at 298 K. Calculate the solubility of BaSO4 in g per 100 cm3 of solution.  solubility of BaSO4 = g per 100 cm3 of solution  The equation for the formation of a gaseous sulfate ion is shown. S+ 2O2+ 2e– → SO4 2–∆H = of SO4 2–Calculate the standard enthalpy change of formation, , of SO4 2–. It may be helpful to draw a labelled energy cycle. Use relevant data from Table1.1 in your calculations. Table 1.1 energy change value / kJ mol–1 lattice energy of barium sulfate, BaSO4–2469 standard enthalpy change of formation of barium sulfate –1473 standard enthalpy change of atomisation of barium +180 first ionisation energy of barium +503 second ionisation energy of barium +965 standard enthalpy change of atomisation of sulfur +279 standard enthalpy change for S→ S2–+440 standard enthalpy change for O→ O2–+657 O=O bond energy +496  of SO4 2–= kJ mol–1 Suggest how the lattice energy of BaSO4differs from the lattice energy of Cs2SO4. Explain your answer. The reaction of solid hydrated barium hydroxide, Ba(OH)2•8H2O, with ammonium salts is endothermic. Calculate the minimum temperature at which the reaction of Ba(OH)2•8H2O with NH4NO3 becomes feasible. Show all your working. Ba(OH)2•8H2O+ 2NH4NO3→ 2NH3+ Ba(NO3)2+ 10H2O= +132 kJ mol–1 ∆S o = +616 J K–1 mol–1  temperature = °C Bariumhydroxide reacts readily with ammoniumchloride on mixing at room temperature. Ba(OH)2•8H2O+ 2NH4Cl → 2NH3+ BaCl 2•2H2O+ 8H2O = +133 kJ mol–1 Some relevant standard entropies are given in Table 1.2. Table 1.2 substance Ba(OH)2•8H2ONH4Cl NH3BaCl 2•2H2OH2OS o / J K–1 mol–1 Calculate the standard Gibbs free energy change, ∆G o, for this reaction at 25 °C. ∆G o = kJ mol–1 
9701_s22_qp_43
THEORY
2022
Paper 4, Variant 3
View
Questions Discovered
275