XMS SEC 3 WA2 2022 MS

3 S3E 2022 WA2 Answers Section A [5 marks] 1 2 3 4 5 A D A C B Section B [20 marks] B1ai sodium sulfate 1 B1aii graphite 1 B1aiii sulfur dioxide & sodium sulfate 1 B1aiv dry ice 1 B1av graphite 1 B1avi dry ice – CO2 sulfur dioxide – SO2 sodium sulfate – Na2SO4 Any one for 1 mark 1 B1b 1 mark for correct number of electrons 1 mark for correct number of atoms. 2 B2ai Using a separating funnel / distillation 1 B2aii Filtration 1 B2aiii Crystallisation 1 B2bi 56oC No marks awarded if unit is missing 1 B2bii 1 mark for both correct arrows 1

4 B2biii 1 mark for shape of graph. 1 mark for labelling axes with boiling points of both substances. 2 B3ai 2Na + 2H2O → H2 + 2NaOH 1 B3aii 2HNO3 + CaO → Ca(NO3)2 + H2O 1 B3aiii 2C3H6 + 9O2 → 6CO2 + 6H2O 1 B3b 1 mark for correct electrons 1 mark for correct charges and ratio 2 B4a Carbon has 4 valence electrons and has a preference for sharing electrons instead of transferring electrons to form a bond. 1 B4bi The higher the relative electron movement speed, the higher the electrical conductivity 1 B4bii Each carbon atom in SWCNT is bonded to three others, while each carbon atom in diamond is bonded to four others. Hence there is one delocalised electron per carbon atom in SWCNT that can help to conduct electricity. 1 1 1 B4ci It is soluble in organic solvents. It has a low electrical conductivity (of 0.00001 S/cm) It has a low melting point of (600 oC) Any 2 2 B4cii C60 1 B4d SWCNT / single-walled carbon nanotube (no marks) It has the highest electrical conductivity among all the carbon allotropes and is also flexible. 1 1