9. The Periodic Table: chemical periodicity
A section of Chemistry, 9701
Listing 10 of 288 questions
Two elements, V and W, are in adjacent groups in the Periodic Table. V reacts with oxygen to form an acidic gas, X. V forms an anion with formula VOm –. W reacts with oxygen to form an acidic gas, Y. W forms an anion with formula WOn 2–. A solution of WOn 2– forms a white precipitate with Ba2+but shows no visible reaction with Mg2+. Complete the table below. identity or value V X m W Y n By referring to enthalpy changes, explain why WOn 2– forms a white precipitate with Ba2+but shows no visible reaction with Mg2+.
9701_m16_qp_42
THEORY
2016
Paper 4, Variant 2
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The table shows information about some of the elements in the third period. element Na Mg Al P S Cl atomic radius / nm 0.186 0.160 0.143 0.110 0.104 0.099 radius of most common ion / nm 0.095 0.065 0.050 0.212 0.184 0.181 maximum oxidation number of the element in its compounds +1 +7 Complete the table to show the maximum oxidation number of each element in its compounds. Explain why the atomic radius of elements in the third period decreases from Na to Cl. The radius of the most common ion of Mg is much smaller than the radius of the most common ion of S. Identify both ions and explain the difference in their radii. Phosphorus is a non-metal in the third period. It reacts vigorously with excess oxygen but slowly with chlorine. Some reactions of phosphorus are shown. phosphorus Aexcess O2reaction 1 Cl 2reaction 2 PCl 5+ HCl Bwater Write an equation to represent reaction 1, the formation of compound A. Give two observations you could make in reaction 2. 1. 2. Name compound B. Cerium is a lanthanoid metal that shows similar chemical reactions to some elements in the third period. Most of cerium’s compounds contain Ce3+ or Ce4+ ions. Cerium shows the same structure and bonding as a typical metal. Draw a labelled diagram to show the structure and bonding in cerium. Cerium(oxide, CeO2, is a ceramic. Suggest two physical properties of cerium(oxide. 1. 2. A naturally occurring sample of cerium contains only four isotopes. Data for three of the isotopes are shown in the table. isotope 136Ce 138Ce 140Ce 142Ce relative isotopic mass 135.907 137.906 139.905 to be calculated percentage abundance 0.185 0.251 88.450 to be calculated The Ar of the sample is 140.116. Use these data to calculate the relative isotopic mass of the fourth isotope in this sample of cerium. Give your answer to three decimal places. relative isotopic mass =
9701_m17_qp_22
THEORY
2017
Paper 2, Variant 2
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Group2 metals form alkaline solutions in water. Write the equation for the reaction of calcium oxide with water. Identify the ion that causes an aqueous solution to be alkaline. The table shows the melting points of some Group2 metal oxides. compound melting point / °C MgO CaO SrO BaO Explain the trend in the melting points of the oxides down Group2. Oxygen reacts readily with some metals, but each Group2 metal requires strong heating to start the reaction with oxygen. Suggest why strong heating is required to start these reactions. Berylliumoxide reacts with hydrochloricacid to form molecules of BeCl 2. Deduce the bond angle in BeCl 2.  Unlike the other oxides of Group2 metals, berylliumoxide is amphoteric. Give the meaning of the term amphoteric. Berylliumoxide and aluminiumoxide have similar chemical properties. The Be(OH)4 2– anion is a product of the reaction between berylliumoxide and excess concentrated OH–. Construct an equation for this reaction. Magnesiumoxide reacts reversibly with chlorine according to the following equation. 2MgO+ 2Cl 22MgCl 2+ O2Under certain conditions, a dynamic equilibrium is established. State two features of a reaction that is in dynamic equilibrium.  The equilibrium constant, Kp, is given by the following expression. Kp = pO2 pCl 2 At 1.00 × 105 Pa and 500 K, 70% of the initial amount of Cl 2has reacted. Calculate Kp and state its units.  Kp =  units =  Magnesiumperoxide, MgO2, is made in the following reaction. MgO+ H2O2MgO2+ H2O∆H = –96 kJ mol–1 compound enthalpy change of formation, ∆Hf / kJ mol–1 MgO–602 H2O2–188 H2O–286 The peroxide ion is O2 2–. Deduce the average oxidation number of oxygen in the peroxide ion. Define the term enthalpy change of formation. Use the data given to calculate the enthalpy change of formation of MgO2. ∆Hf MgO2= kJ mol–1 Magnesium peroxide decomposes slowly to form magnesium oxide and oxygen. MgO2MgO+ 2O2Use your answer to and the data in the table to calculate the enthalpy change of this reaction. If you were unable to obtain an answer to , use the value ∆Hf = –550 kJ mol–1. This is not the correct answer.  enthalpy change of reaction = kJ mol–1 
9701_m20_qp_22
THEORY
2020
Paper 2, Variant 2
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Iron(compounds are generally only stable in neutral, non-oxidising conditions. It is difficult to determine the lattice energy of FeO experimentally. Use data from the Data Booklet and this Born–Haber cycle to calculate the lattice energy, ∆H latt, of FeOin kJ mol–1. Fe2++ O+ 2e– Fe2++ O–+ e– Fe++ O+ e– Fe+ OFeOFe2++ O2–Fe+ 2O21 Fe+ 2O21 –141 kJ mol–1 –272 kJ mol–1 +798 kJ mol–1 +416 kJ mol–1 H latt  ∆H lattFeO= kJ mol–1 Most naturally occurring samples of iron(oxide are found as the mineral wüstite. Wüstite has formula Fe20Ox. It contains both Fe2+ and Fe3+ ions. 90% of the iron is present as Fe2+ and 10% is present as Fe3+. Deduce the value of x.  x = State and explain how the lattice energy of FeOcompares to the lattice energy of CaO. Heating of FeO results in the formation of Fe3O4, as shown. reaction 1 4FeO → Fe + Fe3O4 Each formula unit of Fe3O4 contains one Fe2+ and two Fe3+ ions. Show how reaction1 can be described as a disproportionation reaction. Fe3O4can be electrolysed using inert electrodes to form Fe. Write the half-equation for the reaction that occurs at the anode during the electrolysis of Fe3O4. Calculate the maximum mass of iron metal formed when Fe3O4is electrolysed for sixhours using a current of 50 A. Assume the one Fe2+ and two Fe3+ ions are discharged at the same rate.  mass of iron = g LiFePO4 can be used in lithium-ion rechargeable batteries. When the cell is charging, lithium reacts with a graphite electrode to form LiC6. When the cell is discharging, the half-equations for the two processes that occur are as follows. anode half-equation LiC6 → 6C + Li+ + e– cathode half-equation Li+ + FePO4 + e– → LiFePO4 State one possible advantage of developing cells such as lithium-ion rechargeable batteries. Use the cathode half-equation to determine the change, if any, in oxidation states of lithium and iron at the cathode during discharging. metal change in oxidation state during discharging from to lithium iron  Write the equation for the overall reaction that occurs when this cell is discharging. 
9701_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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