9. The Periodic Table: chemical periodicity
A section of Chemistry, 9701
Listing 10 of 288 questions
Gold is an unreactive metal that can only be oxidised under specific conditions. The standard electrode potential, E o, of Au3+/ Auis +1.50 V. Define the term standard electrode potential. Draw a fully labelled diagram of the apparatus that should be used to measure the standard cell potential, , of Au3+/ Auand HNO3/ NO. Include all necessary chemicals.  Some relevant half-equations and their standard electrode potentials are given. half-equation E o / V Au3++ 3e– Au+1.50 [AuCl 4]–+ 3e– Au+ 4Cl –+1.00 NO3 –+ 4H++ 3e– NO+ 2H2O+0.96 Write an ionic equation to show the spontaneous reaction that occurs when an electric current is drawn from the cell in . Calculate the of the reaction in .  = V Gold can be oxidised by a mixture of concentrated hydrochloricacid and concentrated nitric acid, known as aqua regia. Concentrated hydrochloric acid is 12 mol dm–3. Concentrated nitricacid is 16 mol dm–3. Explain why aquaregia is able to dissolve gold. In your answer, state and explain what effect the use of concentrated hydrochloricacid and concentrated nitricacid have on the E values of half-equations 2 and 3. Aqueous gold(chloride, AuCl 3, reacts with aqueous hydrogenperoxide, H2O2, under certain conditions, forming Au, O2 and HCl. A student carries out separate experiments using different initial concentrations of AuCl 3 and H2O2. The initial rate of each reaction is measured. The table shows the results that are obtained. experiment [AuCl 3] / mol dm–3 / mol dm–3 rate of production of O2/ dm3 minute–1 0.05 0.50 7.66 × 10–2 0.10 0.50 1.53 × 10–1 0.15 1.00 4.60 × 10–1 Write an equation for the reaction of AuCl 3 with H2O2. Determine the rate equation of the reaction. Show your reasoning, quoting data from the table. Use the results of experiment2 to calculate the value of the rate constant, k, for this reaction. Include the units of k.  rate constant, k =  units =  Al F3 is an ionic compound. The Born–Haber cycle for the formation of Al F3 is shown. Al 3++ 3F+ 3e– Al + 3FAl + 1.5F2Al + 1.5F2Al F3Al 3++ 3F–∆H3 ∆H2 ∆H1 ∆H4 ∆H5 ∆H6 Name the enthalpy changes labelled ∆H4 and ∆H6. ∆H4 = ∆H6 =  Use the data in the table and data from the Data Booklet to calculate the lattice energy of Al F3. process enthalpy change / kJ mol–1 Al → Al +326 Al → Al 3++5137 F→ F––328 Al + 1.5F2→ Al F3–1504  lattice energy of Al F3 = kJ mol–1 Scandiumfluoride, ScF3, is an ionic compound. Use data from the Data Booklet to suggest how the lattice energy of Al F3 compares with the lattice energy of ScF3. Explain your answer. Al F3 is sparingly soluble in water. The concentration of its saturated solution at 298 K is 6.5×10–2 mol dm–3. Write an expression for the solubility product, Ksp, of Al F3. Ksp = Calculate the numerical value of Ksp for Al F3 at 298 K.  Ksp =  
9701_m20_qp_42
THEORY
2020
Paper 4, Variant 2
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Use Carbon forms two stable oxides, CO and CO2. Lead forms three oxides: yellow PbO, black PbO2 and red Pb3O4. Carbon monoxide burns readily in air. Heating black lead oxide produces oxygen gas, leaving a yellow residue. Suggest a balanced equation for each reaction. Explain how these two reactions illustrate the relative stabilities of the +2 and +4 oxidation states down Group IV. Red lead oxide contains lead atoms in two different oxidation states. Suggest what these oxidation states are, and calculate the ratio in which they occur in red lead oxide. Predict the equation for the action of heat on red lead oxide. When red lead oxide is heated with dilute nitric acid, HNO3, a solution of lead(nitrate is formed and a black solid is left. Suggest an equation for this reaction. Explain how this reaction illustrates the relative basicities of the two oxidation states of lead. Both tin(oxide and tin(oxide are amphoteric. Write a balanced equation for the reaction between tin(oxide and aqueous sodium hydroxide.
9701_s07_qp_4
THEORY
2007
Paper 4, Variant 0
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Limewater is a saturated solution of Ca(OH)2 in water. It is used to test for the presence of CO2 in a gaseous mixture. Write an equation for the reaction between limewater and CO2. A saturated solution of Ba(OH)2 can be used instead of Ca(OH)2 to test for CO2. A saturated solution of Mg(OH)2 cannot be used for this test. Explain why a saturated solution of Ba(OH)2 can be used to test for CO2. Explain why a saturated solution of Mg(OH)2 cannot be used to test for CO2. Describe and explain the trend in the thermal stabilities of the carbonates down Group 2. Nickel carbonate, NiCO3, decomposes on heating. Use the Data Booklet to explain whether NiCO3 will decompose more or less readily than CaCO3.
9701_s16_qp_41
THEORY
2016
Paper 4, Variant 1
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Limewater is a saturated solution of Ca(OH)2 in water. It is used to test for the presence of CO2 in a gaseous mixture. Write an equation for the reaction between limewater and CO2. A saturated solution of Ba(OH)2 can be used instead of Ca(OH)2 to test for CO2. A saturated solution of Mg(OH)2 cannot be used for this test. Explain why a saturated solution of Ba(OH)2 can be used to test for CO2. Explain why a saturated solution of Mg(OH)2 cannot be used to test for CO2. Describe and explain the trend in the thermal stabilities of the carbonates down Group 2. Nickel carbonate, NiCO3, decomposes on heating. Use the Data Booklet to explain whether NiCO3 will decompose more or less readily than CaCO3.
9701_s16_qp_43
THEORY
2016
Paper 4, Variant 3
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Sodium oxide, Na2O, is a white crystalline solid with a high melting point. Write an equation for the reaction of sodium with oxygen, forming sodium oxide. Include state symbols. Explain why sodium oxide has a high melting point. When sodium oxide reacts with water an alkaline solution is obtained. Explain why the solution obtained is alkaline. You should use the Brønsted-Lowry theory of acids and bases in your answer. Calculate the pH of the solution obtained when 3.10 g of sodiumoxide are added to 400 cm3 of water. pH = Use the data below, and other suitable data from the Data Booklet, to calculate the lattice energy of sodium oxide, Na2O. energy change value / kJ mol–1 standard enthalpy change of formation of sodium oxide, Na2O– 416 standard enthalpy change of atomisation of sodium, Na+109 electron affinity of O–142 electron affinity of O–+844 Na2O= kJ mol–1 State how Na2Sdiffers from Na2O. Indicate this by placing a tick () in the appropriate box in the table. Na2Sis more exothermic than Na2ONa2Sis the same as Na2ONa2Sis less exothermic than Na2OExplain your answer. 
9701_s18_qp_41
THEORY
2018
Paper 4, Variant 1
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