A-LevelChemistryAtoms, molecules and stoichiometry9701/42 · May/June 2017 · Q314 Marks
In a molecule of SOCl2 the sulfur atom has four bonds. Draw a 'dot-and-cross' diagram of SOCl2. Show the outer shell electrons only.
- (a)In a molecule of SOCl2 the sulfur atom has four bonds. Draw a 'dot-and-cross' diagram of SOCl2. Show the outer shell electrons only.[2]
- (b)(i)Write equations for the reactions between NaOH and HCl, NaOH and SO2.[2]
- (b)(ii)Calculate the total number of moles of NaOH that reacted with the SO2 and HCl. moles of NaOH = ...[2]
- (b)(iii)Calculate the number of moles of RCO2H that produced the SO2 and HCl. moles of RCO2H = ...[1]
- (b)(iv)Hence calculate the Mr of the carboxylic acid, RCO2H. Mr RCO2H = ...[1]
- (b)(v)The R group contains carbon and hydrogen only. Suggest the molecular formula of RCO2H.[1]
- (c)(i)Suggest a reagent for step 3.[1]
- (c)(ii)Suggest structures for angelic acid, T and U. angelic acid T U[3]
- (c)(iii)State the type of stereoisomerism shown by angelic acid and T. angelic acid compound T[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [1] four shared pairs: S=O and 2 × S-Cl
- [1] all (9) lone pairs
- [1] NaOH + HCl → NaCl + H2O
- [1] 2NaOH + SO2 → Na2SO3 + H2O
- [1] moles (at start) = 0.5 × 60 / 1000 = 3 × 10⁻² AND moles (at end) = 0.5 × 10.8 / 1000 = 5.4 × 10⁻³
- [1] moles reacted (= (30–5.4) × 10⁻³ =) 2.5 × 10⁻² correct ans. scores [2]
- [1] moles of RCO2H = 2.46 × 10⁻²/3 = 8.2–8.3 × 10⁻³ mole
- [1] Mr = 1.00 / (8.2 × 10⁻³) = 121.95 (=122)
- [1] C7H6O2 OR C6H5CO2H
- [1] LiAlH4
- [3] Structures for angelic acid: (Z)-2-methylbut-2-enoic acid; T: 2-methylbutanoic acid; U: 2-methylbutanamine (shows structures in MS)
- [1] angelic acid: geometrical OR cis-trans compound T: optical
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →