Questions 1
Topic – 4.2 Bonding and structure
(a) Complete Table 1.1 using relevant information from the Periodic Table.
(b) State and explain the difference in the ionic radius of \(Al^{3+}\) compared to \(Mg^{2+}\).
(c) Draw a labelled diagram to show the structure and bonding in sodium.
(d) Fig. 1.1 shows the variation in melting point of some Period 3 elements in their standard states at room temperature and pressure. 
(i) Explain why Si has a high melting point.
(ii) Complete Fig. 1.1 to show the variation in the melting points of the elements P, S and Cl.
(e) Two Period 3 elements react with an excess of oxygen at room pressure.
(i) Complete Table 1.2.
(ii) The solutions made in column 3 of Table 1.2 are mixed together. Name the type of reaction that occurs.
(iii) Write an equation to describe the reaction between P4O10 and an excess of water.
(f) Aluminium hydroxide is amphoteric.
(i) Explain what is meant by amphoteric.
(ii) Write an equation to describe the reaction that occurs when aluminium hydroxide, Al(OH)₃, reacts with NaOH(aq).
▶️Answer/Explanation
Ans:
1(a)
(b) M1 it / \(Al^{3+}\) is smaller (compared to \(Mg^{2+}\))
M2 greater nuclear attraction for remaining electrons
M3 same shielding effect AND greater nuclear charge
(c) 
(d)(i) large amount of energy required to break bonds in giant covalent structure
(ii) acid–base OR neutralisation
(iii) \(P_4O_{10} + 6H_2O→ 4H_3PO_4\)
(f)(i) reacts with both acids and bases OR shows both acidic and basic behaviour
(ii) Al(OH)₃ + NaOH → NaAl(OH)₄
Questions 2
Topic – 5.1 Enthalpy change, ΔH
Separate samples of Na₂CO₃ and NaHCO₃ react with HCl(aq) to produce the same products, as shown in Table 2.1.
(a) Complete the reaction pathway diagram in Fig. 2.1 for reaction 2. Label the diagram to show the enthalpy change, \(∆H_2\), and the activation energy, \(E_A\). 
(b) The value for ∆H1 is determined by experiment using the following method.
• 50.0 cm³ of \(2.00moldm^{–3}\) HCl(aq) is added to a polystyrene cup.
• The initial temperature of the acid is recorded as 19.6°C.
• 0.0400mol of Na₂CO₃ is added and the mixture is stirred.
• All the solid Na₂CO₃ disappears and a colourless solution is produced.
The maximum temperature recorded during the reaction is 26.2°C.
(i) Describe one other observation that shows the reaction is complete.
(ii) Calculate the value of ∆H1 in kJmol⁻¹. Assume the specific heat capacity of the reaction mixture is the same as for water and no heat is lost to the surroundings. Show your working.
(iii) Thermal decomposition occurs when NaHCO₃ is heated.
reaction 3: 2NaHCO₃ → Na₂CO₃+ H₂O + CO₂
Calculate the enthalpy change for reaction 3, \(∆H_r\), using the data in Table 2.1 and the value of \(∆H_1\) calculated in (b)(ii). (If you were unable to calculate a value for \(∆H_1\) in (b)(ii), assume the enthalpy change is \(–38.4kJmol^{–1}\). This is not the correct value.)
(c) Z is a salt that contains a Period 4 element from Group 2. When Z is heated brown gas forms. Identify the formula of Z and use it to write an equation for the reaction.
▶️Answer/Explanation
Ans:
(c) Ca(NO₃)₂ → CaO + 2NO₂ + ½O₂
M1 correct formula for calcium nitrate: Ca(NO₃)₂
M2 correct balanced equation
Questions 3
Topic – 7.1 Chemical equilibria: reversible reactions, dynamic equilibrium
(a) Describe what is meant by dynamic equilibrium.
(b) Reaction 4 describes the reversible reaction between yellow Fe³⁺ (aq) and colourless SCN⁻ (aq) to produce red FeSCN²⁺ (aq).
reaction 4 Fe³⁺(aq) + SCN⁻(aq) \( \rightleftharpoons \) FeSCN²⁺(aq)
yellow colourless red
An equilibrium mixture contains Fe³⁺(aq), SCN⁻ (aq) and FeSCN²⁺ (aq). A few colourless crystals of soluble KSCN(s) are added. The mixture is then left until it reaches equilibrium
again. The temperature of both equilibrium mixtures is the same.
(i) Deduce the changes that occur, if any, in the equilibrium mixture after KSCN(s) is added compared to the original equilibrium mixture.
• change in appearance
• change in relative concentration of Fe³⁺(aq)
• change in value of the equilibrium constant, \(K_c\).
(ii) The expression for the equilibrium constant, \(K_c\), for reaction 4 is shown
\(5.00 × 10^{–5}mol\) of Fe³⁺(aq) and \(5.00 × 10^{–5}mol\) of SCN⁻ (aq) are added together and allowed to reach equilibrium. The total volume of the mixture is 25.0 cm³. At equilibrium the concentration of FeSCN²⁺(aq) is \(4.23 × 10^{–4}moldm^{–3}\). Calculate the equilibrium constant, \(K_c\), for reaction 4. Include the units in your answer.
(c) Determine the full electronic configuration of Fe³⁺.
(d) SCN⁻ (aq) is colourless. Complete the dot-and-cross diagram in Fig. 3.1 to show the arrangement of outer electrons in an SCN⁻ ion.
▶️Answer/Explanation
Ans:
(a) M1 rates of forward and reverse / backward reactions are equal
M2 no change in measurable properties OR concentration of reactants AND products remain constant
(b)(i) M1 change to appearance of the mixture: (goes) darker red / more red
M2 change to relative concentration of Fe³⁺(aq): decreases
M3 change to the value of equilibrium constant, \(K_c\): constant / none
Questions 4
Topic – 13.1 Formulas, functional groups and the naming of organic compounds
CH₃(CH₂)₅CHBrCH₃ exists as a pair of stereoisomers.
(a) Draw the three-dimensional structures of the two stereoisomers of CH₃(CH₂)₅CHBrCH₃. R can be used to represent CH₃(CH₂)₅.
(b) A sample of CH₃(CH₂)₅CHBrCH₃ reacts with NaOH to make CH₃(CH₂)₅CH(OH)CH₃ in an \(S_N1\) mechanism. Complete Fig. 4.1 to show the mechanism for the reaction of CH₃(CH₂)₅CHBrCH₃ and NaOH. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate.
(c) Separate samples of CH₃(CH₂)₅CHBrCH₃, CH₃(CH₂)₅CH(OH)CH₃, and CH₃(CH₂)₅CHCH₂ are tested with different reagents. Complete Table 4.1. If no reaction occurs, write × in the relevant box. 
(d) CH₃(CH₂)₅CHBrCH₃ is heated with D to produce three different molecules, E, F and G.
(i) Name the type of reaction.
(ii) Identify D and the conditions used.
(e) (i) Both σ and π bonds are present in a molecule of E as a result of different types of hybridisation in the carbon atoms. Complete Table 4.2 to show the number of carbon atoms with each type of hybridisation in a molecule of E. 
(ii) Describe the essential feature of an unbranched hydrocarbon that causes its molecules to show stereoisomerism. Explain how this feature leads to stereoisomerism.
▶️Answer/Explanation
Ans:
(a) Three-dimensional stereoisomers of CH₃(CH₂)₅CHBrCH₃
M1 correct representation of left-hand answer as 3d structure of one of the enantiomers of CH₃(CH₂)₅CHBrCH₃
M2 correct representation of 3d structure of the second enantiomer of CH₃(CH₂)₅CHBrCH₃
(ii) M1 presence of a 𝜋 bond
M2 limited rotation of C=C bond
M3 EITHER
two different groups on each / both double-bonded carbon atoms
OR
two different atoms on each / both double-bonded carbon atom
OR
one H / atom and one alkyl group on each / both double-bonded carbon atom
Questions 5
Topic – 22.2 Mass spectrometry
Compound W has the molecular formula \(C_4H_{10}O\). It contains only one functional group.
(a) Table 5.1 shows the two peaks with the greatest m/e values in the mass spectrum of W
(i) Calculate the relative abundance, x, of the peak at m/e = 75 using the information from Table 5.1.
(ii) The mass spectrum of W also shows peaks at m/e = 29 and m/e = 59. Suggest the molecular formulae of these fragments.
(b) A sample of W, \(C_4H_{10}O\), is heated under reflux with an excess of acidified \(K_2Cr_2O_7\) until there is no further reaction. Only one organic product, X, is present in the mixture at the end of the reaction. 
(i) Absorption A is shown in Fig. 5.1. Absorption B is shown in Fig. 5.2. Complete Table 5.3 using the information given in Fig. 5.1, Fig. 5.2 and Table 5.2. 
(ii) Use the information in (a) and (b)(i) to draw the structure of X in the box in Fig. 5.3. 
(c) Y is a structural isomer of W. Both W and Y produce colourless bubbles when sodium is added to them. Y does not react when heated with acidified K₂Cr₂O₇. Y does not react when warmed with alkaline \(I_2 (aq)\).
(i) Name the functional group present in Y.
(ii) Complete the equation to describe the reaction of W or Y with sodium.
(iii) Draw the structure of Y.
▶️Answer/Explanation
Ans: