Question detail

If 4 moles of magnesium oxide (MgO) are produced, how many grams of magnesium are needed?

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. 96 g
B. 48 g
C. 24 g
D. 192 g

Answer

96 g

Explanation

The balanced equation for the reaction shows that 2 moles of magnesium produce 2 moles of MgO. Therefore, 4 moles of MgO require 4 moles of magnesium. The relative formula mass of magnesium is 24 g/mol, so 4 moles x 24 g/mol = 96 g.

Common mistake

Misunderstanding Mole Ratios

Students often confuse the coefficients in a balanced equation as mass ratios instead of mole ratios.

Emphasize that coefficients represent the number of moles of each substance, not their masses. Practice interpreting balanced equations to reinforce this concept.

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