Chemistry · Oct / Nov 2020 · Paper 41 · Question 5
0620
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5(a)(i)[2]
breakdown by (the passage of) electricity (1)
of an ionic compound in molten/aqueous (state) (1)
5(a)(ii)[1]
they do not react
5(a)(iii)[2]
negative electrode: hydrogen (gas) (1)
positive electrode: oxygen (gas) (1)
5(a)(iv)[2]
H+ + e(–) as the only species on the left (1)
equation fully correct (1)
2H+ + 2e(–) → H2 (scores 2)
5(b)(i)[1]
S + O2 → SO2
5(b)(ii)[2]
rate of forward reaction is equal to rate of reverse reaction (1)
constant concentration (of reactants and products) (1)
5(b)(iii)[2]
exothermic / heat / energy is released / surroundings warm up
products have lower energy than reactants / ORA
5(c)[1]
water / H2O
5(d)[2]
(Mr =) 98
(0.75 × 98 =) 73.5
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