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Question
The mass of one molecule of a substance is 4.65 × 10–23 g. What is its molecular mass ? What could this substance be ?
Solution
Given:
Mass of one molecule of a substance = 4.65 × 10-23
We know that the mass of a molecule of a substance is equal to the mass of 1 mole of that substance. 1 mole of a substance consists of 6.022 × 1023 molecules; therefore, the mass of a molecule of a substance is equal to the mass of 6.022 × 1023 molecules.
Therefore, to calculate the molecular mass of the substance, we need to calculate the mass of 6.022 × 1023 molecules of that substance.
Mass of 1 molecule of the substance = 4.65 × 10-23
Mass of 6.022 × 1023 molecules of the substance = 6.022 × 1023 × 4.65 × 10-23 = 28g
Hence, molecular mass of the substance is 28 u.
Nitrogen has a molecular mass of 28 u; therefore, the substance is nitrogen.
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