Chemistry · May / June 2025 · Paper 42 · Question 2
0620
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This question is about covalent compounds.
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2(a)[2]
M1 pair of electrons
M2 electron(s) shared between two atoms
2(b)(i)[2]
M1 the oxidation number of chlorine / Cl
M2 (oxidation number) is +1
2(b)(ii)[3]
M1 O with 1 dot-cross bonding pair with each Cl
M2 4 non-bonding dots for O
M3 6 non-bonding crosses for each Cl
2(b)(iii)[3]
M1 (forces of) attraction between molecules are broken (during boiling)
M2 covalent bonds (between Cl and O atoms) are broken (during thermal decomposition)
M3 weak attraction between molecules and strong covalent bonds / bonding between atoms correctly applied
2(b)(iv)[2]
M1 no ions
M2 no mobile electrons
2(c)(i)[1]
graphite
2(c)(ii)[1]
electrons
2(c)(iii)[2]
M1 5 correct Si atoms
M2 4 correct O atoms
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