11.4. The reactions of chlorine
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 290 questions
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
View
Some reactions of chromium ions are shown below. [Cr(H2O)6]2+[Cr(H2O)6]3+Cr2O7 2–CrO4 2–metal + H2SO4 reaction 1 reaction 2 reaction 3 OH–H3O+Use the Data Booklet to suggest a suitable metal to carry out reaction 1. Use E o values to explain your answer to by calculating the . A student suggested that reaction 2 could be carried out using acidified hydrogen peroxide solution. Use the Data Booklet to show whether or not this reaction is feasible. Explain using oxidation numbers whether or not reaction 3 is a redox reaction. The student used an acidified solution of Cr2O7 2–to electroplate a steel box with chromiummetal. Calculate how long it would take for a current of 0.125 A to deposit 0.0312 g of chromium metal. time =
9701_m16_qp_42
THEORY
2016
Paper 4, Variant 2
View
Calcium and its compounds have a large variety of applications. Calcium metal reacts readily with most acids. Write an equation for the reaction of calcium with dilute nitricacid. State symbols are not required. When calcium metal is placed in dilute sulfuricacid, it reacts vigorously at first. After a short time, a crust of calcium sulfate forms on the calcium metal and the reaction stops. Some of the calcium metal and dilute sulfuricacid remain unreacted. Suggest an explanation for these observations. Calcium ethanedioate is formed when calcium reacts with ethanedioic acid, (CO2H)2. The compound contains one cation and one anion. Draw the ‘dot-and-cross’ diagram of the cation present in calciumethanedioate. Show all electrons.  Draw the displayed formula of the anion present in calciumethanedioate.  Calciumchlorate(, Ca(Cl O)2, is used as an alternative to sodiumchlorate(, NaCl O, in some household products. Suggest a use for calciumchlorate(. The chlorate(ion is formed when cold aqueous sodiumhydroxide reacts with chlorine. Write an ionic equation for this reaction. State symbols are not required. The chlorate(ion is unstable and decomposes when heated as shown. Deduce the oxidation number of chlorine in each species. Complete the boxes. 3Cl O– 2Cl – + Cl O3 – oxidation number of chlorine:  In terms of electron transfer, state what happens to the chlorine in the reaction in . Calciumlactate is used in some medicines. It forms when lacticacid (2-hydroxypropanoicacid) reacts with calciumcarbonate. C lactic acid H CO2H H3C OH Identify the two other products of the reaction of lacticacid with calciumcarbonate. +1 Two possible methods of making lactic acid are shown. reaction 2 reaction 4 reaction 1 reaction 3 lactic acid C O H H3C C O CO2H H3C C H CH2OH H3C OH C H CN H3C OH C H CO2H H3C OH State suitable reagents and conditions for reactions 1 and 3. reaction reagents and conditions  Name the type of reaction that occurs in reaction2. Reaction4 uses NaBH4. Identify the role of NaBH4 in this reaction. Lacticacid has a chiral centre. State what is meant by the term chiral centre. 
9701_m18_qp_22
THEORY
2018
Paper 2, Variant 2
View
Describe the trend in the reactivity of the halogens Cl 2, Br2 and I2 as oxidising agents. Explain this trend using values of E o (X2 / X–) from the Data Booklet. Write an equation for the reaction between chlorine and water. Use standard electrode potential, E o, data from the Data Booklet to calculate the for the following reaction. Cl 2 + 2OH– Cl – + Cl O– + H2O  = V The [OH–] was increased and the Ecell was measured. Indicate how the value of the Ecell measured would compare to the calculated in by placing one tick () in the table. Ecell becomes less positive than . Ecell stays the same as . Ecell becomes more positive than . Explain your answer.  A half-equation involving bromate(ions, BrO3 –, and bromide ions is shown. BrO3 –+ 3H2O+ 6e– Br –+ 6OH–E o = +0.58 V An alkaline solution of chlorate(, Cl O–, can be used to oxidise bromide ions to bromate(ions. Use the Data Booklet and the half-equation shown to write an equation for this reaction. Calculate the for the reaction in .  = V When a concentrated solution of bromic(acid, HBrO3, is warmed, it decomposes to form bromine, oxygen and water only. Write an equation for this reaction. The use of oxidation numbers may be helpful. 
9701_m18_qp_42
THEORY
2018
Paper 4, Variant 2
View
Questions Discovered
290