Question detail

What is the relative formula mass of sodium sulphate, Na₂SO₄ (A-level cue 54a9e8a8 focus)

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

Amount of substance

Question

A. 142.09 g/mol
B. 142.04 g/mol (A-level cue 54a9e8a8 distractor 1)
C. 142.14 g/mol (A-level cue 54a9e8a8 distractor 2)
D. 142.19 g/mol (A-level cue 54a9e8a8 distractor 3)

Answer

142.09 g/mol

Explanation

The correct option is 142.09 g/mol. 142.09 g/mol is correct because it supports the objective: Use relative formula mass for ionic compounds.. The reasoning stays within Relative atomic mass and relative molecular mass and avoids drifting into a similar A-Level Chemistry idea. This version is uniquely anchored to Relative atomic mass and relative molecular mass. Retrieval anchor: A-level cue 54a9e8a8. This item is treated as conceptual revision rather than a formal calculation item because the validated answer is an explanation or option choice, not a worked numerical response.

Common mistake

Misunderstanding Ionic Compounds

Students often confuse the relative formula mass of ionic compounds with that of covalent compounds, leading to incorrect calculations.

To calculate the relative formula mass of an ionic compound, use the formula: Mr = sum(Ar of all ions in the formula). For example, for NaCl: Mr = Ar(Na) + Ar(Cl) = 23 + 35.5 = 58.5 g/mol. Thus, the relative formula mass of NaCl is 58.5 g/mol.

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