Question

The weight of 1 mole of a gas of density $0.1784{\text{ g }}{{\text{L}}^{{\text{ - 1}}}}$ at NTP is?
A.$0.1784{\text{g}}$
B.1 g
C.4 g
D.Cannot be calculated

Answer 1

To answer this question, knowledge of mole concept is required. One mole of a substance is equal to $6.022 \times {10^{23}}$ particles of that substance. This is also equal to the gram atomic mass of an element and the gram molecular mass of a compound. For a gaseous compound, one mole of a gas at standard temperature and pressure has volume of $22.4$ Litre. We shall substitute the appropriate values in the formula given below to calculate the mass of the gas.
Formula Used:
${{M = V \times d}}$
Where M is the mass of the gas, V is the volume occupied by the gas and d is the density of the gas.

Complete step by step answer:
Since one mole of a gas at NTP=$22.4$Litre,
Therefore, mass of the gas having density $0.1784{\text{ g }}{{\text{L}}^{{\text{ - 1}}}}$=$22.4 \times 0.1784 = 3.9916$g.
Approximately equal to 4g.

Hence the correct answer is option C.

Note:
NTP or normal temperature and pressure is equal to ${27^0}{\text{C}}$ or 298 ${\text{K}}$ and 1 atmosphere pressure.
One mole of a substance can also be calculated from the following formula: ${\text{n = }}\dfrac{{\text{m}}}{{\text{M}}}$where m is the mass of the substance in grams and M is the molecular weight.
Definition of one mole- one mole is the amount of any substance that contains the same number of particles as the number of atoms in exactly 12 grams of Carbon-12 isotope.
The concept of mole was introduced because the atoms and molecules were so small that they could not be weighed. .