Questions 1
(a)Topic- 28.2 General characteristic chemical properties of the first set of transition elements, titanium to copper
(b)Topic- 1.2 Isotopes
(c)Topic- 1.2 Isotopes
(d)Topic- 13.4 Isomerism: structural isomerism and stereoisomerism
Cobalt, rhodium and iridium are metals in the same group of the Periodic Table.
(a) The shorthand electronic configuration of cobalt is \([Ar]3d^74s^2\).
(i) Identify what is meant by [Ar] by giving its full electronic configuration.
(ii) The lowest-energy electrons in cobalt are in the 1s orbital. Draw the shape of a 1s orbital.
(iii) Deduce the number of unpaired electrons in a cobalt atom.
(b) Table 1.1 gives some details of the stable naturally occurring isotopes of rhodium and iridium.
Complete Table 1.1.
(c) Table 1.2 shows the relative abundances of isotopes in a sample of an alloy containing rhodium and iridium only.
(i) Define relative isotopic mass.
(ii) Use Table 1.2 to calculate the relative atomic mass, \(A_r\), of iridium in the alloy. Give your answer to two decimal places.
(d) Hydrated rhodium(III) chloride, RhCl₃•xH₂O, catalyses the conversion of ethene to but-2-ene. Both stereoisomers of but-2-ene are formed in the reaction.
(i) Hydrated rhodium(III) chloride contains 20.5% by mass of water of crystallisation. Deduce the integer value of x in RhCl₃•xH₂O. Show your working.
(ii) Define stereoisomers
(iii) Explain how the conversion of ethene to but-2-ene can be described as an addition reaction.
(iv) Draw the two stereoisomers of but-2-ene.
▶️Answer/Explanation
Ans
Questions 2
(a)Topic- 11.1 Physical properties of the Group 17 elements
(b) Topic-13.2 Characteristic organic reactions
(c) Topic-6.1 Redox processes: electron transfer and changes in oxidation number (oxidation state)
Chlorine is one of the elements in Group 17 of the Periodic Table.
(a) (i) Describe the colours of the Group 17 elements, chlorine to iodine, at room temperature.
(ii) Describe the relative reactivity of the elements chlorine to iodine as oxidising agents.
(iii) State what is observed when chlorine reacts with hydrogen.
(iv) Explain why the thermal stability of the hydrogen halides decreases down the group.
(b) The halogenoalkane CH₃CH₂Cl forms when chlorine reacts with C₂H₆ via a free-radical substitution mechanism.
(i) Define free radical.
(ii) State the essential condition for chlorine to react with \(C_2H_6\) at room temperature.
(iii) Write two equations to show the propagation steps in this reaction.
1 ……………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………….
(c) CHCl₃ is another halogenoalkane. CHCl₃ forms when propanone reacts with NaClO. NaClO is made from chlorine in a disproportionation reaction.
(i) Identify a reagent and conditions that can be used to convert chlorine to NaClO.
(ii) Define disproportionation.
(iii) Write numbers in the boxes to balance the equation showing the reaction of propanone with NaClO.
(iv) Aqueous AgNO₃ dissolved in ethanol reacts with an aqueous solution of CHCl₃. State what is observed in this reaction. Explain your answer.
▶️Answer/Explanation
Ans
(a)(i) chlorine = yellow-green
bromine = orange / brown / red
iodine = silver grey / black
(ii) oxidising strength decreases from chlorine to iodine
(iii) green colour disappears
(iv) H—Hal covalent bond strength decreases down the group
(b)(i) a species with one or more unpaired electrons
(ii) ultraviolet
Questions 3
(a)Topic-4.2 Bonding and structure
(b)Topic-10.1 Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
(c) Topic-1.4 Ionisation energy
(d) Topic-3.1 Electronegativity and bonding
(e)Topic-3.1 Electronegativity and bonding
(f)Topic-7.2 Brønsted–Lowry theory of acids and bases
The Group 14 elements show a change from non-metallic to metallic character down the group.
(a) Table 3.1 shows some properties of two Group 14 elements, C and Sn, in their standard states. The table is incomplete.
(i) Complete Table 3.1.
(ii) Identify the lattice structure shown by graphite.
(iii) Explain why Sn has good electrical conductivity.
(b) Carbon is found in inorganic compounds such as carbonates.
(i) Write an equation for the reaction of magnesium carbonate with dilute HCl(aq).
(ii) Describe the thermal stability of the carbonates down Group 2.
(iii) Ammonium carbonate undergoes an acid–base reaction with NaOH(aq). Explain this statement.
(c) Fig. 3.1 shows a sketch of some of the ionisation energies of silicon, Si.
(i) Complete the graph in Fig. 3.1 to show the third to sixth ionisation energies of Si.
(ii) Construct an equation to represent the second ionisation energy of Si.
(d) Fig. 3.2 shows the boiling points of the simplest hydrides of the Group 14 elements, C to Pb.
(i) Explain the trend in the boiling points of the Group 14 hydrides shown in Fig. 3.2.
(ii) Deduce the shape of a molecule of SiH₄.
(e) Silicon readily reacts with elements of high electronegativity.
(i) Write an equation for the formation of SiCl₄ from its constituent elements.
(ii) Describe what is observed when a small sample of SiCl₄ is added to water.
(iii) SiO₂ is a white solid that melts above 1700°C. SiCl₄ is a colourless liquid at room temperature. Explain the difference in the melting points of these two compounds with reference to their structure and bonding.
(f) Tin forms an amphoteric oxide, SnO₂. Suggest the formula of the tin compound that forms when SnO₂ reacts with H₂SO₄ in an acid–base reaction.
▶️Answer/Explanation
Ans
(d)(i) M1 molecules CH4 to PbH4 have greater number of electrons/ number of electrons increase
M2 greater / stronger instantaneous dipole–induced forces / London forces / dispersion forces
OR
more energy required to overcome the instantaneous dipole–induced forces / London forces / dispersion forces
(ii) tetrahedral
(e)(i) Si + 2Cl₂ → SiCl₄
(ii) effervescence / misty / steamy fumes
(iii) M1 SiO₂ is giant covalent
AND
SiCl₄ is simple covalent / simple molecular / molecular
M2 so need less energy to overcome IMF’s in SiCl₄ compared to the bonds in SiO₂ ora
(f) Sn(SO₄)₂
Questions 4
(a)Topic-21.1 Organic synthesis
(b)Topic-21.1 Organic synthesis
(c)Topic-21.1 Organic synthesis
(d)Topic-21.1 Organic synthesis
(e)Topic-21.1 Organic synthesis
(f)Topic-21.1 Organic synthesis
Propanone, CH₃COCH₃, is an important organic reagent. Fig. 4.1 shows some reactions of propanone and its derivatives.
(a) Reaction 1 is a nucleophilic addition reaction.
(i) Complete Fig. 4.2 to show the mechanism for the formation of A from propanone. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate. 
(ii) Explain why A does not show optical isomerism.
(b) Suggest the reagents and conditions for reaction 2.
(c) Reaction 3 is a reduction reaction.
(i) Construct an equation to represent reaction 3. Use [H] to represent one atom of hydrogen from the reducing agent.
(ii) Name C.
(d) State what is observed in reaction 4.
(e) Explain why Fehling’s reagent does not react with propanone.
(f) Compounds A, B and C can be distinguished using infrared spectroscopy.
(i) Explain why the absorptions at 2850–2950 cm⁻¹ are not useful to help determine which of the compounds A, B or C produces the infrared spectrum in Fig. 4.3. Use Table 4.1 to answer this question.
(ii) Identify which of compounds A, B or C produces the infrared spectrum in Fig. 4.3. Explain your answer.
compound …………………………
explanation ………………………………….
▶️Answer/Explanation
Ans
(d) red / orange / yellow ppt
(e) Fehling’s solution cannot oxidise ketones
OR
ketones are not easily oxidised
(f)(i) All three have a C—H
OR
CH bond
(ii) compound A
AND
absorption at 2200–2250 cm⁻¹ indicates C≡N