Question detail

If 80 g of calcium carbonate (CaCO3) decomposes, how many moles of calcium oxide (CaO) are produced?

Try the question, check the answer, then read the explanation to understand the curriculum point.

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At a glance

MCQ

Type

practice

Style

Topic

Use of amount of substance in relation to masses of pure substances

Question

A. 0.5 mol
B. 1.0 mol
C. 1.5 mol
D. 2.0 mol

Answer

0.5 mol

Explanation

The balanced equation for the decomposition of CaCO3 is CaCO3 → CaO + CO2. The relative formula mass of CaCO3 is 100 g/mol. Using moles = mass / Mr, we find that 80 g / 100 g/mol = 0.8 mol of CaCO3, which produces 0.5 mol of CaO.

Common mistake

Using Incorrect Ratios

Students often confuse the ratios of reactants and products in a balanced equation, applying mass ratios instead of mole ratios.

Always refer to the coefficients in the balanced equation to determine mole ratios, and remember that these ratios are not the same as mass ratios.

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