11. Group 17
A section of Chemistry, 9701
Listing 10 of 617 questions
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_43
THEORY
2023
Paper 4, Variant 3
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Spathose is an iron ore that contains iron(carbonate, FeCO3. The percentage of iron(carbonate in spathose can be determined by titration with acidified potassium dichromate(solution using a suitable indicator. The ionic equation is shown below. Cr2O7 2–+ 14H++ 6Fe2+→ 2Cr3++ 6Fe3++ 7H2OA 5.00 g sample of spathose was reacted with excess concentrated hydrochloric acid and then filtered. The filtrate was made up to 250 cm3 in a volumetric flask with distilled water. A 25.0 cm3 sample of the standard solution required 27.30 cm3 of 0.0200 mol dm–3 dichromate(solution for complete reaction. Calculate the amount, in moles, of dichromate(ions used in the titration. amount = mol Use your answer to to calculate the amount, in moles, of Fe2+ present in the 25.0 cm3 sample. amount = mol Use your answer to to calculate the amount, in moles, of Fe2+ present in the 250 cm3 volumetric flask. amount = mol Use your answer to to calculate the mass of iron(carbonate present in the sample of spathose. mass = g Calculate the percentage of iron(carbonate in the sample of spathose. percentage of iron(carbonate = % Iron ores containing iron(compounds can be analysed using a similar method. A standard solution of an aqueous iron(compound is reacted with aqueous tin(chloride. Aqueous tin(chloride and aqueous iron(chloride are the products of this reaction. Write an ionic equation for this reaction. Do not include state symbols. Any excess tin(chloride can be removed by reaction with HgCl 2. A white precipitate of Hg2Cl 2 is produced. Complete the equation for this reaction. ( ) + HgCl 2→ SnCl 4( ) + Hg2Cl 2( )
9701_m16_qp_22
THEORY
2016
Paper 2, Variant 2
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State what is meant by the term partition coefficient. Ammonia is soluble in both water and organic solvents. An aqueous solution of ammonia is shaken with the immiscible organic solvent trichloromethane. The mixture is left to reach equilibrium. Samples are taken from each layer and titrated with dilute hydrochloric acid. ● ● A 25.0 cm3 sample from the trichloromethane layer requires 13.0 cm3 of 0.100 mol dm–3 HCl to reach the end-point. ● ● A 10.0 cm3 sample from the aqueous layer requires 12.5 cm3 of 0.100 mol dm–3 HCl to reach the end-point. Calculate the partition coefficient, Kpartition, of ammonia between trichloromethane and water.  Kpartition = Butylamine, C4H9NH2, is also soluble in both water and organic solvents. Suggest how the value of Kpartition of butylamine between trichloromethane and water would compare to the value of Kpartition calculated in . Explain your answer. Explain why butylamine is basic. Write an equation to show butylamine reacting as a base. State how the basicity of butanamide, C3H7CONH2, compares to that of butylamine. State a reagent for the conversion of butanamide into butylamine. 
9701_m18_qp_42
THEORY
2018
Paper 4, Variant 2
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Use mathematical expressions to define the following terms. ● pH = ● Ka for a weak acid, HA =  Write equations to show how a buffer solution consisting of a mixture of HAand NaAcontrols pH when an acid or an alkali is added. When chlorine dissolves in water the following reaction occurs. Cl 2+ H2OHCl O+ H++ Cl –When solutions of chlorine are used for water purification, the pH of the solution of chlorine is kept near to pH7 by the addition of a base. Chlorine is dissolved in water to produce 1000 cm3 of a solution containing 0.170 mol of HCl O and 0.170 mol of HCl. A buffer solution is then prepared by adding 0.200 mol of NaOHto this solution. The NaOH reacts initially with the HCl. Calculate the pH of the buffer solution. [HCl O is a weak acid with Ka = 2.9 × 10–8 mol dm–3.]  pH = 
9701_m19_qp_42
THEORY
2019
Paper 4, Variant 2
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