11. Group 17
A section of Chemistry, 9701
Listing 10 of 617 questions
Ni2+ ions form a number of different complex ions, including [Ni(H2O)6]2+, [Ni(NH3)6]2+ and 2+. The abbreviation en represents 1,2-diaminoethane. The numerical values of two stability constants, Kstab, are given in Table 5.1. Table 5.1 complex Kstab [Ni(NH3)6 ]2+ 4.8 × 107 2+ 2.0 × 1018 Complete the expression for the Kstab of 2+. Kstab = A solution of [Ni(H2O)6]2+ is added to a solution that contains 0.10 mol dm–3 NH3 and 0.10 mol dm–3 en. Predict which complex ion, [Ni(NH3)6 ]2+ or 2+, is present in the resulting mixture in the highest concentration. Explain your answer. complex ion present in largest concentration = explanation Complete the equation for the ligand exchange reaction occurring in . [Ni(H2O)6]2+ + + Complete to show the three-dimensional structures of the two isomers of 2+. Use N N to represent the en ligand. Name the type of isomerism shown. Ni Ni type of isomerism shown
9701_w24_qp_42
THEORY
2024
Paper 4, 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
Questions Discovered
617