The questions used were June 2007 P2 Q2, Q3, Q4. The answer for Question 2 is given below. Time allowed was 15 minutes to do all three questions.
Results will be posted on http://www.facebook.com/pages/CXC-Chemistry-Lessons/147920055257221?v=wall at the end of today’s session.
Q2 Answers
2(a)(i) Experiment 1 - Reducing agent.
Experiment 2 - Oxidising agent.
2(a)(ii) Experiment 1 - Cr6+ (orange) is converted to Cr3+(green). Chromium gains electrons,
so A acts as a reducing agent.
Experiment 2 - Fe2+(green) is converted to Fe3+(yellow). Iron loses an electron, so A
acts as an oxidizing agent.
2(b)(i) Cu(s) + 2Ag+(aq) ® Cu2+(aq) + 2Ag(s).
2(b)(ii) Cu2+(aq) is blue.
2(c) No change would be observed since copper is not electropositive enough to reduce the iron ions to
the metal.
2(d)(i) Vinegar.
2(d)(ii) Cu2+(s) + CO32-(s) + 2H+(aq) ® Cu2+(aq) + CO2(g) + H2O(l).
1 comment:
i tried dem.... so far i hv 8mrks for Q2 nt sure bout my ans for part a(ii) :S
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