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5070 w12 er.pdf


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Cambridge General Certificate of Education Ordinary Level
5070 Chemistry November 2012
Principal Examiner Report for Teachers
Question 18
The hydroxide ion does combine with hydrogen ions but not with hydrogen, thus option A is incorrect.
Question 22
The strongest distractor in this question was B, Group III. Atoms in Group III lose three electrons when they
form ions and atoms in Group V gain three electrons when they form ions. Thus X in the ion X3- was a
member of Group V.
Question 29
Calcium oxide is a basic oxide, silica is an acidic oxide, and the reaction is an acid-base reaction.
Question 34
Carbon dioxide is responsible for global warming and not carbon monoxide. Thus option A was incorrect.
Question 35
The structures of two compounds were given and were very different. Therefore alternative D, structural
formula, was incorrect. The two compounds each had the molecular formula C4H10 and therefore the same
composition by mass.

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© 2012