Question detail

In Relative formula mass, which option best answers variant 3 of this quantitative chemistry objective: Define relative formula mass, Mr, as the sum of the relative atomic masses of atoms in the numbers shown in a formula?

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

Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations

Question

A. formula and unit: Define relative formula mass, Mr, as the sum of the relative atomic masses of atoms in the numbers shown in a formula
B. wrong formula: uses a different Unit 4.3 relationship from Relative formula mass
C. wrong unit: gives a value without checking the required unit
D. wrong reasoning: confuses coefficients, subscripts, mass, moles, or concentration

Answer

The correct option is formula and unit: Define relative formula mass, Mr, as the sum of the relative atomic masses of atoms in the numbers shown in a formula.

Explanation

The correct option is formula and unit: Define relative formula mass, Mr, as the sum of the relative atomic masses of atoms in the numbers shown in a formula. It is correct because it directly supports the approved learning objective to define relative formula mass, Mr, as the sum of the relative atomic masses of atoms in the numbers shown in a formula. This belongs to Relative formula mass within Chemical measurements, conservation of mass and the quantitative interpretation of chemical equations, so the answer must use the named Unit 4.3 relationship and avoid mixing it with nearby ideas such as mass, moles, concentration, yield, atom economy, gas volume, coefficients, or subscripts.

Common mistake

Confusing Relative Atomic Mass with Relative Formula Mass

Students often confuse relative atomic mass (Ar) with relative formula mass (Mr), thinking they are the same.

Remember that relative atomic mass refers to a single atom, while relative formula mass is the sum of the relative atomic masses of all atoms in a formula.

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For Relative formula mass, which formula choice answer best supports this Unit 4.3 objective: Define relative formula mass, Mr, as the sum of the relative atomic masses of atoms in the numbers shown in a formula?