11.4. The reactions of chlorine
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 290 questions
Write a balanced equation for the reaction of each of the following chlorides with water. phosphorus(chloride silicon(chloride When sulfur is heated under pressure with chlorine, the major product is SCl2 (Cl-S-Cl). S8+ 8Cl28SCl2Use data from the Data Booklet to calculate the enthalpy change, ∆H, for this reaction. The eight sulfur atoms in the S8 molecule are all joined in a single ring by single bonds. ∆H = kJ mol–1 Under suitable conditions, SCl2 reacts with water to produce a yellow precipitate of sulfur and a solution A. Solution A contains a mixture of SO2and compound B. What is the oxidation number of sulfur in SCl2? Work out how the oxidation number of sulfur changes during the reaction of SCl2 with water. Suggest the identity of compound B. Construct an equation for the reaction between SCl2 and water. What would you observe when each of the following reagents is added to separate samples of solution A? AgNO3K2Cr2O7
9701_w10_qp_41
THEORY
2010
Paper 4, Variant 1
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The electrolytic purification of copper can be carried out in an apparatus similar to the one shown below. impure copper anode anode ‘sludge’ pure copper cathode CuSO4 The impure copper anode contains small quantities of metallic nickel, zinc and silver, together with inert oxides and carbon resulting from the initial reduction of the copper ore with coke. The copper goes into solution at the anode, but the silver remains as the metal and falls to the bottom as part of the anode ‘sludge’. The zinc also dissolves. Write a half equation including state symbols for the reaction of copper at the anode. Use data from the Data Booklet to explain why silver remains as the metal. Use data from the Data Booklet to predict what happens to the nickel at the anode. Write a half equation including state symbols for the main reaction at the cathode. Use data from the Data Booklet to explain why zinc is not deposited on the cathode. Suggest why the blue colour of the electrolyte slowly fades as the electrolysis proceeds. Most of the current passed through the cell is used to dissolve the copper at the anode and precipitate pure copper onto the cathode. However, a small proportion of it is ‘wasted’ in dissolving the impurities at the anode which then remain in solution. When a current of 20.0 A was passed through the cell for 10.0 hours, it was found that 225 g of pure copper was deposited on the cathode. Calculate the following, using appropriate data from the Data Booklet. • number of moles of copper produced at the cathode • number of moles of electrons needed to produce this copper • number of moles of electrons that passed through the cell Hence calculate the percentage of the current through the cell that has been ‘wasted’ in dissolving the impurities at the anode. Nickel often occurs in ores along with iron. After the initial reduction of the ore with coke, a nickel-iron alloy is formed. Use data from the Data Booklet to explain why nickel can be purified by a similar electrolysis technique to that used for copper, using an impure nickel anode, a pure nickel cathode, and nickel sulfate as the electrolyte. Explain what would happen to the iron during this process.
9701_w10_qp_41
THEORY
2010
Paper 4, Variant 1
View
Write a balanced equation for the reaction of each of the following chlorides with water. phosphorus(chloride silicon(chloride When sulfur is heated under pressure with chlorine, the major product is SCl2 (Cl-S-Cl). S8+ 8Cl28SCl2Use data from the Data Booklet to calculate the enthalpy change, ∆H, for this reaction. The eight sulfur atoms in the S8 molecule are all joined in a single ring by single bonds. ∆H = kJ mol–1 Under suitable conditions, SCl2 reacts with water to produce a yellow precipitate of sulfur and a solution A. Solution A contains a mixture of SO2and compound B. What is the oxidation number of sulfur in SCl2? Work out how the oxidation number of sulfur changes during the reaction of SCl2 with water. Suggest the identity of compound B. Construct an equation for the reaction between SCl2 and water. What would you observe when each of the following reagents is added to separate samples of solution A? AgNO3K2Cr2O7
9701_w10_qp_42
THEORY
2010
Paper 4, Variant 2
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The electrolytic purification of copper can be carried out in an apparatus similar to the one shown below. impure copper anode anode ‘sludge’ pure copper cathode CuSO4 The impure copper anode contains small quantities of metallic nickel, zinc and silver, together with inert oxides and carbon resulting from the initial reduction of the copper ore with coke. The copper goes into solution at the anode, but the silver remains as the metal and falls to the bottom as part of the anode ‘sludge’. The zinc also dissolves. Write a half equation including state symbols for the reaction of copper at the anode. Use data from the Data Booklet to explain why silver remains as the metal. Use data from the Data Booklet to predict what happens to the nickel at the anode. Write a half equation including state symbols for the main reaction at the cathode. Use data from the Data Booklet to explain why zinc is not deposited on the cathode. Suggest why the blue colour of the electrolyte slowly fades as the electrolysis proceeds. Most of the current passed through the cell is used to dissolve the copper at the anode and precipitate pure copper onto the cathode. However, a small proportion of it is ‘wasted’ in dissolving the impurities at the anode which then remain in solution. When a current of 20.0 A was passed through the cell for 10.0 hours, it was found that 225 g of pure copper was deposited on the cathode. Calculate the following, using appropriate data from the Data Booklet. • number of moles of copper produced at the cathode • number of moles of electrons needed to produce this copper • number of moles of electrons that passed through the cell Hence calculate the percentage of the current through the cell that has been ‘wasted’ in dissolving the impurities at the anode. Nickel often occurs in ores along with iron. After the initial reduction of the ore with coke, a nickel-iron alloy is formed. Use data from the Data Booklet to explain why nickel can be purified by a similar electrolysis technique to that used for copper, using an impure nickel anode, a pure nickel cathode, and nickel sulfate as the electrolyte. Explain what would happen to the iron during this process.
9701_w10_qp_42
THEORY
2010
Paper 4, Variant 2
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Questions Discovered
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