11. Group 17
A section of Chemistry, 9701
Listing 10 of 617 questions
Data should be selected from Table3.1 in order to answer some parts of this question. Table 3.1 electrode reaction E o / V Cl 2 + 2e– 2Cl – +1.36 2HOCl + 2H+ + 2e– Cl 2 + 2H2O +1.64 Cl O– + H2O + 2e– Cl – + 2OH– +0.89 Sn4+ + 2e– Sn2+ +0.15 Sn2+ + 2e– Sn –0.14 V2+ + 2e– V –1.20 V3+ + e– V2+ –0.26 VO2+ + 2H+ + e– V3+ + H2O +0.34 VO2 + + 2H+ + e– VO2+ + H2O +1.00 Standard electrode potentials are measured under standard conditions. Describe the standard conditions used in the Sn4+ / Sn2+ half-cell. Complete the diagram below to show how E o (Sn4+ / Sn2+) can be measured experimentally. Your diagram should be fully labelled to identify all apparatus and substances.  Equal volumes of 1.0 mol dm–3 Sn2+and 1.0 mol dm–3 Cl –are mixed. Use relevant E o values to explain whether a reaction occurs between these two ions. Equal volumes of 1.0 mol dm–3 of Sn2+and acidified 1.0 mol dm–3 VO2+are mixed. Write an equation for the reaction that takes place in the resulting mixture. A solution of SnCl 2is electrolysed for a measured time using a steady current. A mass of 2.95 g of tin metal is produced at the cathode. Al 2O3is electrolysed for the same time by the same current. Calculate the mass of aluminium metal produced at the cathode. Give your answer to three significant figures. Show your working.  mass of aluminium metal = g 
9701_w22_qp_41
THEORY
2022
Paper 4, Variant 1
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An aqueous solution of copper(sulfate is a blue colour due to the presence of [Cu(H2O)6]2+ complex ions. Write an equation for the reaction between [Cu(H2O)6]2+ ions and NaOH. Write an equation for the reaction between [Cu(H2O)6]2+ ions and an excess of conc.HCl. If an excess of ammonia is added to a solution of [Cu(H2O)6]2+ a deep blue solution containing [Cu(NH3)4(H2O)2]2+ complex ions is formed. There are two possible stereoisomers with the formula [Cu(NH3)4(H2O)2]2+. Complete the diagrams to show the two stereoisomers in the boxes below. isomer 1 isomer 2 Cu Cu  Use your answer in to deduce whether each of these isomers is polar or non-polar. polarity of isomer 1 polarity of isomer 2  The numerical value of the stability constant, Kstab, of the [Cu(NH3)4(H2O)2]2+ complex ion is 1.40×1013. Define stability constant. Compare the stabilities of the [Cu(H2O)6]2+ and [Cu(NH3)4(H2O)2]2+ complex ions. Explain your answer. Write an expression for the stability constant, Kstab, of the [Cu(NH3)4(H2O)2]2+ complex ion. State the units of the stability constant. Kstab =  units =  In a particular solution the concentration of the [Cu(NH3)4(H2O)2]2+ complex ion is 0.0074moldm–3 and the concentration of NH3 is 0.57 mol dm–3. Use your expression in and the Kstab value of 1.40×1013 to calculate the concentration of the [Cu(H2O)6]2+ complex ion in this solution.  concentration of [Cu(H2O)6]2+ = mol dm–3 Phenanthroline, C12H8N2, and ethanedioate ions, C2O4 2–, are bidentate ligands. Ruthenium(ions, Ru3+, form an octahedral complex with phenanthroline and chloride ions. The complex ion contains two phenanthroline molecules. Iron(ions, Fe3+, form an octahedral complex with ethanedioate ions only. Deduce the formula and charge of each of these complex ions. Ru3+ complex Fe3+ complex  
9701_w22_qp_41
THEORY
2022
Paper 4, Variant 1
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Data should be selected from Table3.1 in order to answer some parts of this question. Table 3.1 electrode reaction E o / V Cl 2 + 2e– 2Cl – +1.36 2HOCl + 2H+ + 2e– Cl 2 + 2H2O +1.64 Cl O– + H2O + 2e– Cl – + 2OH– +0.89 Sn4+ + 2e– Sn2+ +0.15 Sn2+ + 2e– Sn –0.14 V2+ + 2e– V –1.20 V3+ + e– V2+ –0.26 VO2+ + 2H+ + e– V3+ + H2O +0.34 VO2 + + 2H+ + e– VO2+ + H2O +1.00 Standard electrode potentials are measured under standard conditions. Describe the standard conditions used in the Sn4+ / Sn2+ half-cell. Complete the diagram below to show how E o (Sn4+ / Sn2+) can be measured experimentally. Your diagram should be fully labelled to identify all apparatus and substances.  Equal volumes of 1.0 mol dm–3 Sn2+and 1.0 mol dm–3 Cl –are mixed. Use relevant E o values to explain whether a reaction occurs between these two ions. Equal volumes of 1.0 mol dm–3 of Sn2+and acidified 1.0 mol dm–3 VO2+are mixed. Write an equation for the reaction that takes place in the resulting mixture. A solution of SnCl 2is electrolysed for a measured time using a steady current. A mass of 2.95 g of tin metal is produced at the cathode. Al 2O3is electrolysed for the same time by the same current. Calculate the mass of aluminium metal produced at the cathode. Give your answer to three significant figures. Show your working.  mass of aluminium metal = g 
9701_w22_qp_43
THEORY
2022
Paper 4, Variant 3
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An aqueous solution of copper(sulfate is a blue colour due to the presence of [Cu(H2O)6]2+ complex ions. Write an equation for the reaction between [Cu(H2O)6]2+ ions and NaOH. Write an equation for the reaction between [Cu(H2O)6]2+ ions and an excess of conc.HCl. If an excess of ammonia is added to a solution of [Cu(H2O)6]2+ a deep blue solution containing [Cu(NH3)4(H2O)2]2+ complex ions is formed. There are two possible stereoisomers with the formula [Cu(NH3)4(H2O)2]2+. Complete the diagrams to show the two stereoisomers in the boxes below. isomer 1 isomer 2 Cu Cu  Use your answer in to deduce whether each of these isomers is polar or non-polar. polarity of isomer 1 polarity of isomer 2  The numerical value of the stability constant, Kstab, of the [Cu(NH3)4(H2O)2]2+ complex ion is 1.40×1013. Define stability constant. Compare the stabilities of the [Cu(H2O)6]2+ and [Cu(NH3)4(H2O)2]2+ complex ions. Explain your answer. Write an expression for the stability constant, Kstab, of the [Cu(NH3)4(H2O)2]2+ complex ion. State the units of the stability constant. Kstab =  units =  In a particular solution the concentration of the [Cu(NH3)4(H2O)2]2+ complex ion is 0.0074moldm–3 and the concentration of NH3 is 0.57 mol dm–3. Use your expression in and the Kstab value of 1.40×1013 to calculate the concentration of the [Cu(H2O)6]2+ complex ion in this solution.  concentration of [Cu(H2O)6]2+ = mol dm–3 Phenanthroline, C12H8N2, and ethanedioate ions, C2O4 2–, are bidentate ligands. Ruthenium(ions, Ru3+, form an octahedral complex with phenanthroline and chloride ions. The complex ion contains two phenanthroline molecules. Iron(ions, Fe3+, form an octahedral complex with ethanedioate ions only. Deduce the formula and charge of each of these complex ions. Ru3+ complex Fe3+ complex  
9701_w22_qp_43
THEORY
2022
Paper 4, Variant 3
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Cobalt(nitrate, Co(NO3)2, is a reddish-brown crystalline solid. It dissolves in water to form a solution containing [Co(H2O)6]2+ complex ions. Complete Table 4.1 giving the formula of the cobalt-containing species that is formed in each of the three reactions described. Table 4.1 reaction reagent added to [Co(H2O)6]2+cobalt-containing species formed NaOH2 an excess of NH33 an excess of conc. HCl Describe the colour change seen in reaction 3. original colour of [Co(H2O)6]2+final colour after addition of an excess of conc. HCl Calcium nitrate, Ca(NO3)2, is a white crystalline solid. When heated, it starts to decompose at approximately 500°C. Write an equation for the decomposition of Ca(NO3)2. Suggest temperatures at which Mg(NO3)2 and Ba(NO3)2 start to decompose. Explain your answer. temperature at which Mg(NO3)2 starts to decompose °C temperature at which Ba(NO3)2 starts to decompose °C explanation
9701_w23_qp_41
THEORY
2023
Paper 4, Variant 1
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Transition elements behave as catalysts and can form complex ions. Explain why transition elements behave as catalysts. Silver forms the linear complex ion [Ag(CN)2]–. Copper forms the tetrahedral complex ion [Cu(CN)4]3−. Titanium forms the complex , where diars is a neutral bidentate ligand. State the oxidation state and the coordination number of titanium in . oxidation state coordination number Draw three-dimensional diagrams to show the shapes of [Ag(CN)2]– and [Cu(CN)4]3−, in the boxes. Label one bond angle on each diagram. Ag Cu The numerical value of the stability constant, Kstab, of the copper(complex [Cu(CN)4]3– is 2.0 × 1027. Write an expression for the Kstab of [Cu(CN)4]3−. Kstab = In a solution the concentrations of CN− and [Cu(CN)4]3− are both 0.0010 mol dm−3. Use your expression from and the value of Kstab to calculate the concentration of Cu+in this solution. concentration of Cu+= mol dm–3 A piece of a copper-containing alloy has a mass of 0.567 g. It is dissolved in an acid giving 100.0 cm3 of a blue solution in which all the copper is present as Cu2+ ions. An excess of KIis added to a 25.0 cm3 sample of this solution. All of the copper is precipitated as white CuI. Cu2+ ions are the only component in the solution that react with KI. This is reaction 1. reaction 1 2Cu2+ + 4I− 2CuI + I2 The liberated I2 is then titrated with 0.0200 mol dm–3 S2O3 2−. This is reaction 2. reaction 2 I2 + 2S2O3 2– 2I− + S4O6 2– The titration requires 20.10 cm3 of 0.0200 mol dm–3 S2O3 2– to reach the end-point. Calculate the number of moles of I2 that are reduced in this titration. number of moles of I2 = mol Calculate the number of moles of copper in the original piece of alloy. number of moles of copper = mol Calculate the percentage of copper in the alloy. percentage of copper = % Suggest why a solution of Cu2+ is coloured but solid CuI is white.
9701_w23_qp_41
THEORY
2023
Paper 4, Variant 1
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Five ligands are listed in Table 6.1. Table 6.1 ligand type of ligand NH3 EDTA4− CN− H2NCH2CH2NHCH2CH2NH2 tridentate C2O4 2− Complete Table 6.1 using the words monodentate, bidentate and polydentate only. Each of these three words may be used once, more than once, or not at all. The molecule H2NCH2CH2NHCH2CH2NH2 is a tridentate ligand. Suggest the meaning of tridentate ligand. Suggest how H2NCH2CH2NHCH2CH2NH2 acts as a tridentate ligand. Nickel forms the octahedral complex [Ni2(H2O)2]2+. This complex can exist in three isomeric forms, listed in Table 6.2. One of these forms is a trans isomer, the other forms are two different cis isomers. Table 6.2 isomer polarity trans isomer cis isomer 1 cis isomer 2 Complete Table 6.2 using the terms polar or non-polar. Each term may be used once, more than once, or not at all. Describe the difference between cis isomer 1 and cis isomer 2.
9701_w23_qp_41
THEORY
2023
Paper 4, Variant 1
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Cobalt(nitrate, Co(NO3)2, is a reddish-brown crystalline solid. It dissolves in water to form a solution containing [Co(H2O)6]2+ complex ions. Complete Table 4.1 giving the formula of the cobalt-containing species that is formed in each of the three reactions described. Table 4.1 reaction reagent added to [Co(H2O)6]2+cobalt-containing species formed NaOH2 an excess of NH33 an excess of conc. HCl Describe the colour change seen in reaction 3. original colour of [Co(H2O)6]2+final colour after addition of an excess of conc. HCl Calcium nitrate, Ca(NO3)2, is a white crystalline solid. When heated, it starts to decompose at approximately 500°C. Write an equation for the decomposition of Ca(NO3)2. Suggest temperatures at which Mg(NO3)2 and Ba(NO3)2 start to decompose. Explain your answer. temperature at which Mg(NO3)2 starts to decompose °C temperature at which Ba(NO3)2 starts to decompose °C explanation
9701_w23_qp_43
THEORY
2023
Paper 4, Variant 3
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Transition elements behave as catalysts and can form complex ions. Explain why transition elements behave as catalysts. Silver forms the linear complex ion [Ag(CN)2]–. Copper forms the tetrahedral complex ion [Cu(CN)4]3−. Titanium forms the complex , where diars is a neutral bidentate ligand. State the oxidation state and the coordination number of titanium in . oxidation state coordination number Draw three-dimensional diagrams to show the shapes of [Ag(CN)2]– and [Cu(CN)4]3−, in the boxes. Label one bond angle on each diagram. Ag Cu The numerical value of the stability constant, Kstab, of the copper(complex [Cu(CN)4]3– is 2.0 × 1027. Write an expression for the Kstab of [Cu(CN)4]3−. Kstab = In a solution the concentrations of CN− and [Cu(CN)4]3− are both 0.0010 mol dm−3. Use your expression from and the value of Kstab to calculate the concentration of Cu+in this solution. concentration of Cu+= mol dm–3 A piece of a copper-containing alloy has a mass of 0.567 g. It is dissolved in an acid giving 100.0 cm3 of a blue solution in which all the copper is present as Cu2+ ions. An excess of KIis added to a 25.0 cm3 sample of this solution. All of the copper is precipitated as white CuI. Cu2+ ions are the only component in the solution that react with KI. This is reaction 1. reaction 1 2Cu2+ + 4I− 2CuI + I2 The liberated I2 is then titrated with 0.0200 mol dm–3 S2O3 2−. This is reaction 2. reaction 2 I2 + 2S2O3 2– 2I− + S4O6 2– The titration requires 20.10 cm3 of 0.0200 mol dm–3 S2O3 2– to reach the end-point. Calculate the number of moles of I2 that are reduced in this titration. number of moles of I2 = mol Calculate the number of moles of copper in the original piece of alloy. number of moles of copper = mol Calculate the percentage of copper in the alloy. percentage of copper = % Suggest why a solution of Cu2+ is coloured but solid CuI is white.
9701_w23_qp_43
THEORY
2023
Paper 4, Variant 3
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Questions Discovered
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