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Questions 1

(a) Topic – 1.4 Ionisation energy

(b)Topic – 1.1 Particles in the atom and atomic radius

(c)Topic -2.4 Reacting masses and volumes (of solutions and gases)

(d)Topic – 4.2 Bonding and structure

(e)Topic -5.1 Enthalpy change, ΔH

The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl . The first ionisation energy of S is not shown.

(a) (i) Complete Table 1.1 to show the number of electrons in the 3p subshell and the total number of unpaired electrons in an atom of P, S and Cl .
(ii) Construct an equation to represent the first ionisation energy of P.
(iii) Three possible values for the first ionisation energy of S are given.
1000 kJ/mol,  1160 kJ/mol, 1320 kJ/mol
Circle the correct value.
Explain your choice by comparing your chosen value to those of P and Cl .

(b) \(P^{3–}\), \(S^{2–}\) and \(Cl^–\) have the same number of electrons.
(i) Give the full electronic configuration of P3–.

(ii) State the trend in ionic radius shown by \(P^{3–}\), \(S^{2–}\) and \(Cl^–\). Explain your answer.
(c) A student does three tests on separate samples of NaCl (aq). Complete Table 1.2 with the observations the student makes in each test.

(d) POCl₃ shows similar chemical properties to PCl₅. POCl₃ has a melting point of 1°C and a boiling point of 106°C. POCl₃ reacts vigorously with water, forming misty fumes and an acidic solution.
(i) Explain how the information in (d) suggests the structure and bonding of POCl₃ is simple covalent.
(ii) Construct an equation for the reaction of POCl₃ with water.
POCl₃ + …………………………… \(to\) ………………………………………………………………………….
(iii)POCl₃ contains a double covalent bond between P and O. Complete the dot-and-cross diagram, in Fig. 1.1, to show the bonding in POCl₃. Show outer shell electrons only.

(e) POCl₃(g) forms when PCl₃(g) reacts with O₂(g).
\(2PCl_3(g) + O_2(g) \to 2POCl_3(g)\)
Table 1.3 gives some relevant data

(i) Define enthalpy change of formation, \(\Delta H_f\).
(ii) Calculate the bond energy of P=O in POCl₃ using the data in Table 1.3. Show your working

▶️Answer/Explanation

Ans:

(ii) \(P(g) \to P^+(g) + e^{(–)}\)

(iii) 1000 (kJmol⁻¹) 
(S) less / least / lowest nuclear attraction (to outer electrons) (than P OR Cl)
OR
nuclear attraction for Cl is stronger (compared to S (and or P))
S less nuclear charge than Cl
OR
Cl has a greater nuclear charge than S
(S has a greater nuclear charge (of outer electrons) than P BUT)
S has two electrons in a (3)p orbital AND resulting in spin-pair repulsion
(b)(i) \(1s^2 2s^2 2p^6 3s^2 3p^6\) 
(ii) ● decreases (from \(P^{3−}\) to \(Cl^−\))
● increased attraction (of outer e−) for nucleus owtte
● increased nuclear charge
● same shielding

(c) (Br₂) no visible reaction
OR
colourless to orange / brown / yellow solution
(conc. \(H_2SO_4\)) no visible reaction
OR
Solution remains colourless
(dil. AgNO₃) white precipitate forms 
(d)(i) (relatively low melting and boiling points suggests) weak intermolecular / VdW forces 
(vigorous reaction with water suggests) hydrolysis 
(ii) POCl₃ + 3H₂O → H₃PO₄ + 3HCl

(e)(i) enthalpy change when one mole of a compound / substance is formed 
from its constituent elements in their standard states 
(ii) 2(–592) = 2(–289) + (496) – 2(P=O)
OR
(2) P=O = 2(–289) + (496) + 2(592)
EP= O = ½(1102) = +551 (kJ mol⁻¹)

Questions 2

(a) Topic – 25.1 Acids and bases

(b)Topic -10.1 Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds

(c)Topic -36.1 Organic synthesis

Barium hydroxide, Ba(OH)₂, is a strong base used in inorganic and organic reactions. Fig. 2.1 shows a reaction scheme involving Ba(OH)₂.

(a) (i) State the variation in solubilities of group 2 hydroxides.
(ii) State what is observed in reaction 1.
(iii) Suggest a reactant for reaction 2.
(iv) Identify A.
(v) Ba(OH)₂ is made by the reaction of Ba with water. Write an equation for this reaction.

(b) The mineral barytocalcite contains both BaCO₃ and CaCO₃. Both compounds decompose on heating.
(i) State which compound decomposes first when barytocalcite is heated. Explain your answer.
(ii) Construct an equation for the complete thermal decomposition of barytocalcite. The formula of barytocalcite is BaCa(CO₃)₂.
BaCa(CO₃)₂ …………………………
(c) Ba(OH)₂ is used to hydrolyse organic compounds. Fig. 2.2 shows the reaction of B with Ba(OH)₂, followed by acidification. Draw the structures of the organic products of the process shown in Fig. 2.2

▶️Answer/Explanation

Ans: 

(a)(i) increases down the group 
(ii) white solid disappears 
(iii) CO₂ / carbon dioxide 
(iv) Ba(CH₃COO)₂ / barium ethanoate 
(v) Ba + 2H₂O → Ba(OH)₂ + H₂
(b)(i) CaCO₃ AND thermal stability of carbonates increases down the group 
(ii) BaCa(CO₃)₂ → BaO + CaO + 2CO₂

Questions 3

(a) Topic – 6.1 Redox processes: electron transfer and changes in oxidation number (oxidation state)

(b)Topic – 10.1 Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds

(c)Topic -11.4 The reactions of chlorine 

(d)Topic -4.1 The gaseous state: ideal and real gases and pV = nRT 

(e) Topic-21.1 Organic synthesis

Potassium chlorate, KClO₃, is widely used as an oxidising agent and to make O₂(g).
(a) Define oxidising agent.
(b) KClO₃(s) decomposes when heated. MnO₂(s) catalyses the exothermic decomposition reaction. Complete and label the diagram in Fig. 3.1 to show the effect of MnO₂(s) on the decomposition of KClO₃(s).

(c) When KClO₃ is heated without a catalyst, KClO₄ and KCl form.
4KClO₃ \(\to\) 3KClO₄ + KCl
Explain why this reaction is described as a disproportionation reaction.

(d) Molten KClO₃ reacts with glucose, C₆H₁₂O₆.
4KClO₃ + C₆H₁₂O₆ → 6CO₂ + 6H₂O + 4KCl
KClO₃ melts at 630K. At this temperature, both CO₂ and H₂O are gases.
(i) Use the ideal gas equation to calculate the volume, in m³, of one mole of gas at 630 K and \(1.00 × 10^5 Pa\). Show your working. Give your answer to 3 significant figures

(ii) 5.00g of C₆H₁₂O₆ reacts completely with molten KClO₃. Use your answer to (d)(i) to calculate the total volume of gas released at 630K and \(1.00 × 10^5 Pa\) in this reaction. (If you were unable to answer (d)(i), use 0.0463 m³ in this question. This is not the correct answer to (d)(i).)

(e) The structure of glucose, C₆H₁₂O₆, is shown in Fig. 3.2.

(i) Complete Table 3.1 to identify the number of primary, secondary and tertiary alcohol groups present in the structure shown in Fig. 3.2.

(ii) Separate samples of aqueous glucose are tested with the reagents shown in Table 3.2. Complete Table 3.2 with the observation for each reaction. Write “no reaction” if applicable.

(iii) There are many structural isomers of \(C_6H_{12}O_6\). Define structural isomers.

▶️Answer/Explanation

Ans: 

(a) compound / molecule / substance that oxidises another / is reduced

(c) Cl / chlorine is both oxidised and reduced

(d)(i) pV = nRT ∴ V = 8.31 × 630 × 100 000 = 0.0524 (m³) 
(ii) moles of gas = 12 × 5.00 / 180 
volume of gas = M1 × (d)(i) = 0.0175 (m³) 
(e)(i) 1 4 0 
(ii) Solution turns from purple to colourless 
Orange / red precipitate forms 
no reaction 
(iii) molecules with the same molecular formula but different structural formulae

Questions 4

(a) Topic -2.3 Formulas

(b)Topic -22.2 Mass spectrometry

(c)Topic -21.1 Organic synthesis

(d)Topic -21.1 Organic synthesis

(e)Topic-21.1 Organic synthesis

Compounds C and D are alkenes with the same molecular formula, C₅H₁₀.

(a) (i) Give the systematic name of D.
(ii) Explain why C and D do not show geometrical (cis/trans) isomerism.
(iii) Draw the structure of a molecule that is a positional isomer of C and D

(iv) Give the structural formula of the compound formed when D reacts with H₂(g) in the presence of a Pt catalyst.
(v) C can form an addition polymer. Draw the structure of one repeat unit of this addition polymer.

(b) The mass spectrum of C shows a molecular ion peak at m/e = 70. This peak has a relative intensity of 48.7. The relative intensity of the [M+1] peak is 2.7. Show that this information is consistent with the molecular formula of C.
(c) C and D both react with HBr.
(i) C reacts with HBr to form E. Complete the diagram in Fig. 4.2 to show the mechanism for this reaction. Draw the structure of the organic intermediate. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate.

(ii) D reacts with HBr to produce F, a chiral bromoalkane. Draw the structure of F.

(iii) Explain why the reaction of HBr with C and D produces different major products.

(d) C can be used to form H

One possible synthesis of H is shown in Fig. 4.5. Different portions of C are used in reactions 1 and 3. Some of the products are then combined to produce H. Fig. 4.5 does not show any of the inorganic products of the reactions.

Complete Table 4.1 with the reagents and conditions required for each of the reactions shown in Fig. 4.5.

▶️Answer/Explanation

Ans: 

a(i) 3-methylbut-1-ene 
(ii) one end / one C of the C=C bond has the same groups attached

(b) \(\frac{2.7}{48.7} \times \frac{100}{1.1}=5(.04)\)

\(M_r = 5 \times 12 + 10 \times 1 = 70\)

(iii) ●C has a tertiary carbocation and a 2ndry carbocation
●D has a secondary carbocation and a primary carbocation
● alkyl groups have a +ve / positive / +I / inductive effect
● more alkyl groups / more inductive effects give a more stable intermediate / carbocation / C+
● In C tertiary carbocation is more stable than the secondary carbocation
Any two ● for 1 mark
Any four ● for 2 mark

(d) (reaction 2) NaOH(aq) 
(reaction 3) hot acidified concentrated KMnO₄ 
(reaction 4) conc H₂SO₄ catalyst

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