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9701 ON 21 P41

Q1

Lindsay JC2G

> Q = num of electrons x elementary charge

> Q = It

> ΔS = ΔSp - ΔSr

> ΔG = ΔH - TΔS

Q2

Lindsay JC2G

> pKa = -logKa

> Ka = 10^(-PKa)

> pH = pKa + log([salt]/[acid])

> pH cannot be maintained when ions have been neutralised, so H+ is in excess

Q3

Lindsay JC2G

> Electron affinity is the enthalpy change when 1 mole of gaseous atom gains 1 mole of electrons

> first affinity is negative because of attraction between protons from the nucleus and electrons

> second affinity is positive because of repulsion of -1 ion and electrons

> greater charge density = greater attraction

Q4

Lindsay JC2G

> greater attraction = larger ionic radius/less polarises

> Δsol = Δhyd - Δlatt

Q5

Lindsay JC2G

> ligand exchange steps

> bidentate ligand is a specie that donates 2 lone pairs to form 2 dative bonds to a transition metal/metal ion

Q6

Lindsay JC2G

> some transition elements are coloured because of d-d orbital splitting. Electrons at lower energy are excited and promoted to a higher level. Wavelength of frequency of light is absorbed and the colour of light not absorbed is seen

> colour remains white when d orbital is full and no splitting occurs

> more (+) E° is stronger oxidising agent, more (-) E° is stronger reducing agent

Q7

Lindsay JC2G

> phenylethanoic acid is most acidic since negative inductive electron withdrawing effect on C=O weakens O-H and stabilises anion

> phenol is the 2nd most acidic since oxygen lone pair becomes delocalised into the ring by overlapping its pi bonding system which weakes O-H bond and stabilises ion

> ethanol is least acidic since electron donating alkyl group strengthens O-H bond and destabilises ion

> conditions and reagent for bromination is UV light and Br2

> to make nitrile, ethanolic KCN and heat is needed

> nitrile to COOH, dil HCl and heat is needed

Q8

Lindsay JC2G

> phenlyamine can react with bromine while ethlamine can’t

> 2,4,6-tribromophenylamine is formed after bromination of phenylamine

Q9

Lindsay JC2G

> following reagents and conditions can be used for reaction of phenylethanoic acid to acyl chloride

-> PCl5 in room temp (most commonly used since no harmful gases are formed and can be kept in room temp

-> PCl2 + heat

-> SOCl3 in room temp (least commonly used since SO2 and HCl are formed which are harmful gases)

> acyl chloride + ethylamine forms amide and hydrogen chloride gas

> reduction of amide requires LiAlH4 in dry ether and forms amine

> triplet when CH2

Q10

Lindsay JC2G

> acidic: H+ reacts with COO- of zwitterions which produces COO-

> NH2 amino acid groups react with H+ to form NH3+ groups

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1. Stochiometry, enthalpy calculation and gibbs free energy.
2. pH calculations
3. definitions along with theory about electron affinity and energy calculations
4. lattice energy, solubility and hydration. Thermal stability.
5. Ligands, ligand exchange and ligand complex isomers
6. Transition metals, why they give off colour, E cell calculation relating to feasibility
7. Benzene compounds and reactions of benzene
8. Benzene and its reaction with Br
9. Benzene compound reactions, Carbon NMR and proton NMR
10. Amino acids and their ions

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9701 PAPER 4 P41 OCT NOV 2021 DISCUSSION COMPLETE CAIE CIE CAMBRIDGE A LEVELS