9. The Periodic Table: chemical periodicity
A section of Chemistry, 9701
Listing 10 of 288 questions
Some oxides of elements in Period3 are shown. Na2O Al 2O3 P4O6 P4O10 SO2 SO3 Na reacts with O2 to form Na2O. Na is the reducing agent in this reaction. Define reducing agent. Write an equation for the reaction of Na2O with water. Al 2O3 is an amphoteric oxide found in bauxite. State what is meant by amphoteric. Al 2O3 is purified from bauxite in several steps. The first step involves heating Al 2O3 with an excess of NaOH. A colourless solution forms. Write an equation for this reaction. Al 2O3 is used as a catalyst in the dehydration of alcohols. State the effect of using Al 2O3 as a catalyst in the dehydration of alcohols. Use the Boltzmann distribution in Fig.2.1 to help explain your answer. energy number of molecules P4O6 is a white solid that has a melting point of 24 °C. Solid P4O6 reacts with water to form H3PO3. Deduce the type of structure and bonding shown by P4O6. Explain your answer. Determine the oxidation number of P in H3PO3. When P4O6is heated with oxygen it forms P4O10. P4O6+ 2O2→ P4O10∆Hr = –1372 kJ mol–1 The enthalpy change of formation, ∆Hf, of P4O10is –3012 kJ mol–1. Calculate the enthalpy change of formation, ∆Hf, of P4O6. ∆Hf of P4O6= kJ mol–1 Write an equation for the reaction of P4O10 with water. SO2 and SO3 are found in the atmosphere. The oxidation of SO2 to SO3 in the atmosphere is catalysed by NO2. The first step of the catalytic oxidation is shown in equation1. equation 1 SO2+ NO2SO3+ NOConstruct an equation to show how NO2 is regenerated in the catalytic oxidation of SO2. NO2 can also react with unburned hydrocarbons to form photochemical smog. State the product of this reaction that contributes to photochemical smog. Fig.2.2 shows how the temperature of the atmosphere varies with height from the ground. –120 –100 –80 –60 –40 temperature / C –20 height / km The equilibrium reaction in equation1 has ∆Hr = –168 kJ mol–1. Suggest how the position of this equilibrium differs at a height of 20 km compared with a height of 50 km from the ground. Explain your answer. 
9701_m22_qp_22
THEORY
2022
Paper 2, Variant 2
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Titanium is a transition element in Period4. It is commonly found as TiO2 in minerals. Define transition element. Identify two typical properties of transition elements.  The TiO2+ ion forms when TiO2 reacts with an excess of sulfuric acid. TiO2+ can be reduced by zinc metal in acidic conditions to form a purple solution containing Ti3+. TiO2+is a colourless ion. Suggest why. Give the electronic configuration of an isolated Ti3+ ion. 1s2 ��������������������������������������������������������������������������������������������������������������������������������� Write an ionic equation for the reduction of TiO2+ by zinc metal in acidic conditions. Acidified Ti3+reacts with oxygen dissolved in water as shown. 4Ti3+ + O2 + 2H2O → 4TiO2+ + 4H+ ∆G o = –436.1 kJ mol–1 The standard reduction potential, E o, of O2 + 4H+ + 4e– 2H2O is +1.23 V. Calculate the standard reduction potential, E o, in V, of the TiO2+/ Ti3+half-cell. Show your working.  E o = V When aqueous citrate ions, C6H5O7 3–, are added to Ti3+, the [Ti(C6H5O7)2]3–complex forms. Explain, in terms of d-orbitals, why Ti3+ is able to form complex ions. Acidified [Ti(C6H5O7)2]3–does not react with oxygen dissolved in water, unlike acidified Ti3+. Suggest what this means for the value of the standard reduction potential, E o, of the following half‑cell. [Ti(C6H5O7)2]2–+ e– [Ti(C6H5O7)2]3–Explain your answer. Some reactions of TiO2 are shown in Fig.3.1. The anion, acac–, is a bidentate ligand. TiO2 TiF6 2– HF Cl 2 TiCl 4 Ti2Cl 2 acac– The titanium ions in TiF6 2– and Ti2Cl 2 have a coordination number of 6. State what is meant by coordination number. Write an equation for the formation of TiF6 2– from TiO2. State what is meant by bidentate ligand. Ti2Cl 2 shows both optical and geometrical (cis/trans) isomerism. Ti2Cl 2 exists as three stereoisomers. The structure of one stereoisomer of Ti2Cl 2 is shown in Fig.3.2. acac acac Ti stereoisomer 1 Cl Cl Complete the structures of the other two stereoisomers of Ti2Cl 2. stereoisomer 2 Ti stereoisomer 3 Ti  The acac– anion is symmetrical. Deduce which, if any, of stereoisomers 1, 2 and 3 in are polar. Explain your answer. 
9701_m22_qp_42
THEORY
2022
Paper 4, Variant 2
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Chlorine, Cl 2, reacts with many elements and compounds to form chlorides. Table 2.1 shows information about some chlorides of Period 3 elements. Table 2.1 Na Mg Si formula of chloride structure of chloride giant bonding of chloride covalent pH of solution formed on addition of chloride to water 6.2 Complete Table 2.1. When Cl 2 reacts with cold NaOH, Cl 2 is both oxidised and reduced. The products are NaCl, water and G. State the type of redox reaction in which the same species is both oxidised and reduced. Identify G. Write an equation for the reaction between Cl2 and hot NaOH. Describe fully what is observed when AgNO3is added to the aqueous solution of the chloride of sodium, followed by dilute NH3. An excess of Cl 2 reacts with phosphorus to form PCl 5. PCl 5 is a simple molecule in the gas phase. It also exists in a solid form as two ions, PCl4 + and PCl 6 –. Complete Table 2.2 to identify the shapes of each of these species. Table 2.2 species PCl5 PCl4 + PCl6 – shape tetrahedral PCl5 reacts with J to form H3PO4. Identify J and state the type of reaction. J type of reaction Cl 2 reacts readily with propene to form K, 1,2-dichloropropane. K can be used to form L. Cl2 Cl Cl Cl propene K L reaction 1 reaction 2 Complete to show the mechanism for the reaction of Cl 2 with propene in reaction 1. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. C H H H CH3 C C C CH3 H H H Cl Cl Cl Cl Identify the reagent and conditions for reaction 2. Draw one repeat unit of the addition polymer that forms from L.
9701_m24_qp_22
THEORY
2024
Paper 2, Variant 2
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