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UPSC NDA II 2024 General Ability Paper

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Question : 60 of 150

Marks: +1, -0

The mass of 0.5 mole of

N_{2}

gas is

7 g
14 g
21 g
28 g

Solution:

Concept:

Molar mass and mole relationship.

One mole of any substance has a mass equal to its molar mass in grams.

Explanation:

The molar mass of

\mathrm{N}_2

gas is

2 \times 14 = 28 \; \text{g/mol}

.

Mass of a sample is given by:

\text{mass} = \text{number of moles} \times \text{molar mass}

.

Substitute:

\text{mass} = 0.5 \; \text{mol} \times 28 \; \text{g/mol} = 14 \; \text{g}

.

Thus, 0.5 mole of

\mathrm{N}_2

gas weighs 14 grams.

Answer:

14 g

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