11. Group 17
A section of Chemistry, 9701
Listing 10 of 617 questions
Define the term transition element. State how the melting point and density of iron compare to those of calcium. Define the term standard cell potential, . Draw a fully labelled diagram of the apparatus that can be used to measure the cell potential of a cell composed of a Cu(/Cu electrode and an Fe(/Fe(electrode. Include all necessary reactants.  The reaction between S2O8 2–and I –is catalysed by adding a few drops of Fe3+. Use equations to show the catalytic role of Fe3+ in this reaction.  Fe3+can oxidise I –, whereas [Fe(CN)6]3–cannot oxidise I –. Use E o values to explain these observations. When aqueous solutions of S2O8 2– and tartrate ions are mixed the reaction proceeds very slowly. However, this reaction proceeds quickly in the presence of an Fe3+catalyst. The overall equation for this reaction is shown. tartrate ions + 3S2O8 2– + 2H2O 2CO2 + 2HCO2 – + 6H+ + 6SO4 2– OH OH CO2 – –O2C Suggest why this reaction is slow without the Fe3+ catalyst. Use the overall equation to deduce the half-equation for the oxidation of tartrate ions, C4H4O6 2–, to carbondioxide, CO2, and methanoate ions, HCO2 –. C4H4O6 2– +  Complete the following table to show the structures of the organic products formed when tartaric acid reacts separately with each reagent. Identify each type of reaction. tartaric acid OH OH CO2H HO2C reagent structure of organic product type of reaction an excess of LiAl H4 an excess of CH3COCl  Tartaric acid reacts with the amine 1-phenylethylamine, C6H5CH(NH2)CH3, to form an ionicsalt. Draw the structure of the salt formed in this reaction. Include the charges on the ions.  
9701_s21_qp_41
THEORY
2021
Paper 4, Variant 1
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Samples of [Cu(H2O)6]2+ are reacted separately with an excess of aqueous sodiumhydroxide or with an excess of aqueous ammonia. Give the following information about these reactions. reaction 1: [Cu(H2O)6]2+ with an excess of aqueous of sodium hydroxide colour and state of the copper-containing species ionic equation type of reaction  reaction 2: [Cu(H2O)6]2+ with an excess of aqueous ammonia colour and state of the copper-containing species ionic equation type of reaction  Copper(oxide is added to hot dilute sulfuricacid. A blue solution, X, and a red-brown solid, Y, form. Suggest the identities of X and Y. Name the type of reaction. X Y type of reaction  
9701_s21_qp_41
THEORY
2021
Paper 4, Variant 1
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An aqueous solution of chromium(contains the green [Cr(H2O)6]3+ complex ion. Complete the electronic configuration of an isolated, gaseous Cr3+ ion. 1s2 ��������������������������������������������������������������������������������������������������������������������������������� Define the term complex ion. [Cr(H2O)6]3+shows some similar chemical properties to [Co(H2O)6]2+. Samples of [Cr(H2O)6]3+ are reacted separately with either NaOH, H2O2, or excess NH3. Use this information and the Data Booklet to suggest the formula of the chromium species formed. State the type of reaction taking place in each case. reagent added to [Cr(H2O)6]3+formula of chromium species formed type of reaction NaOHH2O2an excess of NH3 [Cr(H2O)6]2+ and [Cr2(O2CCH3)4(H2O)2] are both complexes of chromium(and have different colours. Explain why the colours of these complexes are different. The structure of [Cr2(O2CCH3)4(H2O)2] is shown. Ethanoate ions act as ligands in this complex. The ethanoate ligand, CH3CO2 –, is shown as O O. Cr O O O H2O O O O O OH2 O Cr Water and ethanoate ions behave as different types of ligand in this complex. Suggest an explanation for this statement. Deduce the coordination number of Cr and the geometry around each Cr atom in this structure. coordination number geometry around Cr atom ���������������������������������������������������������������������������������������������������  State the type of bond between the two atoms in the Cr–Cr bond. The [Cr2(O2CCH3)4(H2O)2] complex reacts with aqueous acid to form Cr2+ions. Cr2+ions react with O2under acidic conditions. Cr3+ions are formed. Use the Data Booklet to answer the following questions. Construct an ionic equation for the reaction of Cr2+with O2under acidic conditions. Calculate for the reaction in .  = V 
9701_s21_qp_42
THEORY
2021
Paper 4, Variant 2
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Define the term standard electrode potential. Three redox systems, A, B and C, are shown. The ligand 1,2-diaminoethane, H2NCH2CH2NH2, is represented by en. A [Ru(H2O)6]3+ + e– [Ru(H2O)6]2+ B [Ru(NH3)6]3+ + e– [Ru(NH3)6]2+ C 3+ + e– 2+ Two electrochemical cells are set up to compare the standard electrode potentials, E o, of three half-cells. The diagrams show the relative potential of each electrode. [Ru(NH3)6]3+ [Ru(NH3)6]2+ salt bridge V 3+ 2+ + – Pt Pt [Ru(H2O)6]3+ [Ru(H2O)6]2+ salt bridge V 3+ 2+ + – Pt Pt Use this information to complete the table by adding the labels A, B and C to deduce the order of E o for the three half-cells. E o redox system most negative least negative  The complex 3+ shows stereoisomerism. The ligand en is bidentate. Draw three-dimensional diagrams to show the two isomers of 3+. Represent the ligand en by using N N . Name the type of stereoisomerism. isomer 1 Ru isomer 2 Ru type of stereoisomerism  An electrochemical cell consists of a Br2/Br – half-cell and a Ag+/Ag half-cell, under standard conditions. Use the Data Booklet to calculate the . Deduce the direction of electron flow in the wire through the voltmeter between these two half-cells. = V direction of electron flow from to ����������������������������������������� Water is added to the Ag+/Ag half-cell in . Suggest the effect of this addition on the Ecell. Place a tick ( ) in the appropriate box. less positive no change more positive Explain your answer. Silver bromide, AgBr, dissolves in an aqueous solution of S2O3 2– ions to form the complex ion [Ag(S2O3)2]3–. The S2O3 2– ions act as monodentate ligands. equilibrium 1 AgBr+ 2S2O3 2–[Ag(S2O3)2]3–+ Br –Define the term ligand. Write an expression for the equilibrium constant, Kc, for equilibrium1. Kc =  Some additional data are given about the dissolution of AgBr in S2O3 2–. equilibrium constant numerical value solubility product, Ksp, of AgBr 5.4 × 10–13 stability constant, Kstab, of [Ag(S2O3)2]3– 2.9 × 1013 Use your answer to and these data to calculate Kc for equilibrium1. Include the units for Kc.  Kc = units The numerical values for the stability constants, Kstab, of two other silver(complexes are given. silver(complex numerical value of Kstab [Ag(CN)2]– 5.3 × 1018 [Ag(NH3)2]+ 1.6 × 107 An aqueous solution containing Ag+ is added to a solution containing equal concentrations of CN–, NH3and S2O3 2–. The mixture is left to reach equilibrium. Deduce the relative concentrations of [Ag(CN)2]–, [Ag(NH3)2]+ and [Ag(S2O3)2]3– present in the resulting mixture. Explain your answer. > > highest concentration lowest concentration 
9701_s21_qp_42
THEORY
2021
Paper 4, Variant 2
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Define the term transition element. State how the melting point and density of iron compare to those of calcium. Define the term standard cell potential, . Draw a fully labelled diagram of the apparatus that can be used to measure the cell potential of a cell composed of a Cu(/Cu electrode and an Fe(/Fe(electrode. Include all necessary reactants.  The reaction between S2O8 2–and I –is catalysed by adding a few drops of Fe3+. Use equations to show the catalytic role of Fe3+ in this reaction.  Fe3+can oxidise I –, whereas [Fe(CN)6]3–cannot oxidise I –. Use E o values to explain these observations. When aqueous solutions of S2O8 2– and tartrate ions are mixed the reaction proceeds very slowly. However, this reaction proceeds quickly in the presence of an Fe3+catalyst. The overall equation for this reaction is shown. tartrate ions + 3S2O8 2– + 2H2O 2CO2 + 2HCO2 – + 6H+ + 6SO4 2– OH OH CO2 – –O2C Suggest why this reaction is slow without the Fe3+ catalyst. Use the overall equation to deduce the half-equation for the oxidation of tartrate ions, C4H4O6 2–, to carbondioxide, CO2, and methanoate ions, HCO2 –. C4H4O6 2– +  Complete the following table to show the structures of the organic products formed when tartaric acid reacts separately with each reagent. Identify each type of reaction. tartaric acid OH OH CO2H HO2C reagent structure of organic product type of reaction an excess of LiAl H4 an excess of CH3COCl  Tartaric acid reacts with the amine 1-phenylethylamine, C6H5CH(NH2)CH3, to form an ionicsalt. Draw the structure of the salt formed in this reaction. Include the charges on the ions.  
9701_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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Samples of [Cu(H2O)6]2+ are reacted separately with an excess of aqueous sodiumhydroxide or with an excess of aqueous ammonia. Give the following information about these reactions. reaction 1: [Cu(H2O)6]2+ with an excess of aqueous of sodium hydroxide colour and state of the copper-containing species ionic equation type of reaction  reaction 2: [Cu(H2O)6]2+ with an excess of aqueous ammonia colour and state of the copper-containing species ionic equation type of reaction  Copper(oxide is added to hot dilute sulfuricacid. A blue solution, X, and a red-brown solid, Y, form. Suggest the identities of X and Y. Name the type of reaction. X Y type of reaction  
9701_s21_qp_43
THEORY
2021
Paper 4, Variant 3
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Questions Discovered
617