A-LevelChemistryElectrochemistryOct/Nov 2013Paper 1 Q161 Mark
Solid potassium halides react with concentrated sulfuric acid, according to the following equations. reaction 1 2KCl + H2SO4 → K2SO4 + 2HCl reaction 2 2KBr + 2H2SO4 → K2SO4 + SO2 + Br2 + 2H2O reaction 3 8KI + 5H2SO4 → 4K2SO4 + H2S + 4I2 + 4H2O What is the largest change in the oxidation number of sulfur in each of these reactions?
A0 (reaction 1), 0 (reaction 2), 4 (reaction 3)
B0 (reaction 1), 2 (reaction 2), 4 (reaction 3)
C0 (reaction 1), 2 (reaction 2), 8 (reaction 3)
D0 (reaction 1), 4 (reaction 2), 8 (reaction 3)
✓ Correct Answer
The correct answer is C. This question tests the candidate's understanding of electrochemistry within the Chemistrysyllabus. The examiner's mark scheme requires...
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Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
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