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CAIE A Level Chemistry 9701 · Atoms, molecules and stoichiometry

Atoms, molecules and stoichiometry: compare question

Compare5 marksStandard

A student investigates two reactions.

Reaction A: CaCOX3(s)+2 HCl(aq)→CaClX2(aq)+COX2(g)+HX2O(l)\ce{CaCO3(s) + 2HCl(aq) -> CaCl2(aq) + CO2(g) + H2O(l)} The student reacts 5.00 g of CaCOX3\ce{CaCO3} with 25.0 cm3^3 of 2.00 mol dm−3^{-3} HCl\ce{HCl}.

Reaction B: NX2(g)+3 HX2(g)→2 NHX3(g)\ce{N2(g) + 3H2(g) -> 2NH3(g)} The student reacts 5.00 g of NX2\ce{N2} with 5.00 g of HX2\ce{H2}.

Compare the approaches required to determine which reactant is limiting in each reaction. Your answer should include reference to the types of data needed and how the mole concept is applied.

0 words · 5 marks

No account needed for your first marks. Your answer is used only to mark it.

How this question is marked

5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.

Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.

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