Question detail

Calculate the percentage by mass of oxygen in sulfuric acid (H2SO4).

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. 64%
B. 32%
C. 50%
D. 48%

Answer

64%

Explanation

The percentage by mass of oxygen is calculated as follows: Mr of H2SO4 = 2(1) + 32 + 4(16) = 98. The mass of oxygen = 4(16) = 64. Therefore, percentage = (64/98) x 100 = 64%.

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?