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MHTCET 16 May 2024 Shift 2 Paper

Question : 100 of 150

Marks: +1, -0

Calculate mass in kg of 2.5 mole ammonia.

Solution:

Concept:

Mass of a substance is calculated by multiplying the number of moles by its molar mass, then converting grams into kilograms.

Explanation:

Ammonia is

\mathrm{NH}_3

Molar mass of

\mathrm{NH}_3 = 14 + (3 \times 1) = 17\ \mathrm{g\,mol^{-1}}

Mass of

2.5

moles

= 2.5 \times 17 = 42.5\ \mathrm{g}

Now convert grams to kilograms:

42.5\ \mathrm{g} \times \frac{1\ \mathrm{kg}}{1000\ \mathrm{g}} = 0.0425\ \mathrm{kg}

Expressing in scientific notation:

0.0425\ \mathrm{kg} = 4.25 \times 10^{-2}\ \mathrm{kg}

Answer:

4.25 \times 10^{-2}\ \mathrm{kg}

(Option B).

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