11.4. The reactions of chlorine
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 290 questions
Chlorine, Cl 2, is a reactive yellow-green gas. It is a strong oxidising agent. State how Cl 2 is used in water purification. Chlorine has the highest first ionisation energy of the Period3 elements Na to Cl. Construct an equation for the first ionisation energy of chlorine. Include state symbols. Explain the general increase in the first ionisation energies of the Period3 elements. The halide ions, X– (where X = Cl, Br, , show clear trends in their physical and chemical properties. State and explain the relative thermal stabilities of the hydrogen halides, HX. The halide ions react easily with concentrated H2SO4. The main sulfur-containing product of each reaction is shown in the table. halide ion Cl – Br – I– main sulfur-containing product of reaction with concentrated H2SO4 HSO4 – SO2 H2S oxidation number of sulfur Complete the table to show the oxidation number of sulfur in each of the sulfur-containing products. Explain why different sulfur-containing products are produced when each of these halide ions reacts with concentrated H2SO4. Cl 2 reacts with aqueous sodium hydroxide in a disproportionation reaction. State what is meant by disproportionation. Write an equation for the reaction of Cl 2 with cold aqueous sodium hydroxide. Aluminium reacts with chlorine to form aluminium chloride. Aluminium chloride can exist as the gaseous molecule Al 2Cl 6. This molecule contains coordinate bonds. Draw a diagram that clearly shows all the types of bond present in Al 2Cl 6. Describe what you would see when solid aluminium chloride reacts with water. Name the type of reaction that occurs. 0.020 mol of elementZ reacts with excess Cl 2 to form 0.020 mol of a liquid chloride. The liquid chloride has formula ZCl n, where n is an integer. ZCl n reacts vigorously with water at room temperature to give an acidic solution and a white solid. When excess AgNO3is added to the solution, 11.54 g of AgCl forms. Suggest the type of bonding and structure shown by ZCl n. Calculate the value of n in ZCl n.  n = Dichloromethane, CH2Cl 2, is widely used as an organic solvent. CH2Cl 2 can be prepared by reacting CH3Cl and Cl 2 at room temperature. The reaction proceeds via several steps, as shown. initiation Cl 2 2Cl • propagation 1 Cl • + CH3Cl HCl + •CH2Cl propagation 2 Cl 2 + •CH2Cl products final step Cl • + •CH2Cl CH2Cl 2 Give the name of the mechanism of this reaction. State the essential condition required for the initiation step to take place. Give the electronic configuration of Cl •. 1s2 Identify the products of the step labelled propagation2. Name the type of reaction shown in the final step. Suggest the identity of another organic molecule that is a product of the reaction of CH3Cl and Cl 2 under the same conditions. 
9701_m21_qp_22
THEORY
2021
Paper 2, Variant 2
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Iodates are compounds that contain the IO3 – anion. The IO3 – anion is shown. O O O– I Explain, with reference to the qualitative model of electron-pair repulsion, why the IO3 – anion has a pyramidal shape. The reaction of iodine and hot aqueous sodiumhydroxide is similar to that of chlorine and hotaqueous sodiumhydroxide. Sodiumiodate, NaIO3, is formed as one of the products. Suggest an equation for the reaction of iodine and hot aqueous sodiumhydroxide. The decomposition of hydrogen peroxide, H2O2, is catalysed by acidified IO3 –. H2O2 reduces acidified IO3 – as shown. 5H2O2 + 2H+ + 2IO3 – → I2 + 5O2 + 6H2O This reaction is followed by the oxidation of I2 by H2O2. half-equation E o / V H2O2 + 2H+ + 2e– 2H2O +1.77 IO3 – + 6H+ + 5e– 2I2 + 3H2O +1.19 O2 + 2H+ + 2e– H2O2 +0.68 Use the data to show that the separate reactions of H2O2 with IO3 – and with I2 are both feasible under standard conditions. In your answer, give the equation for the reaction of H2O2 with I2. Write the overall equation for the decomposition of H2O2 catalysed by acidified IO3 –. A student collects some data for the reaction of H2O2 with acidified IO3 –, as shown in the table. experiment / mol dm–3 [IO3 –] / mol dm–3 [H+] / mol dm–3 initial rate of reaction / mol dm–3 s–1 0.0500 0.0700 0.025 1.47 × 10–5 0.100 0.0700 0.050 2.94 × 10–5 0.100 0.140 0.025 5.88 × 10–5 0.150 0.140 0.025 8.82 × 10–5 Use the data to determine the order of reaction with respect to , [IO3 –] and [H+]. Show your reasoning. order with respect to = order with respect to [IO3 –] = order with respect to [H+] =  Use your answer to to write the rate equation for this reaction. rate = ���������������������������������������������������������������������������������������������������������������������������� Calculate the value of the rate constant, k, using data from experiment4 and your answer to . Give the units of k.  k =  units =  Pb(IO3)2 is only sparingly soluble in water at 25 °C. The solubility product, Ksp, of Pb(IO3)2 is 3.69 × 10–13 mol3 dm–9 at 25 °C. Write an expression for the solubility product of Pb(IO3)2. Ksp =  Calculate the solubility, in mol dm–3, of Pb(IO3)2 at 25 °C.  solubility = mol dm–3 NH4IO3 is an unstable compound that readily decomposes when warmed. The decomposition reaction is shown. NH4IO3→ 1 2N2+ 1 2O2+ 1 2I2+ 2H2O ∆H = –154.6 kJ mol–1 Use the data in the table to calculate the entropy change of reaction, ∆S, of the decomposition of NH4IO3. compound S / J K–1 mol–1 NH4IO342 N2192 O2205 I2261 H2O70  ∆S = J K–1 mol–1 This reaction is feasible at all temperatures. Explain why, using the data in and your answer to . 
9701_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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Questions Discovered
290