Question

Molecular mass of $N{a_2}S{O_4}.10{H_2}O$ is :
A. $320$
B. $321$
C. $322$
D. $324$

Answer 1

Hint : The molecular mass of a compound is defined as the sum of the atomic masses of the atoms that form the compound. The common name for $N{a_2}S{O_4}.10{H_2}O$ is Sodium Sulphate decahydrate. It is used for the production of detergents and for paper pulping in the kraft process. Glauber's salt is the common name for sodium sulphate decahydrate. It comes in the form of monoclinic crystals that are white or colourless.

Complete Step By Step Answer:
One mole of $N{a_2}S{O_4}.10{H_2}O$ contains one mole of $N{a_2}S{O_4}$ and $10$ moles of ${H_2}O$ .
One mole of $N{a_2}S{O_4}$ contains:
$2mol$ $Na$ $= 2 \times 22.9g = 45.98g$
$1mol$ $S$ $$ $= 1 \times 32.07g = 32.07$
$4mol$ $O$ $= 4 \times 16g = 64g$
Total mass of one mole of $N{a_2}S{O_4} = 142.68g$
One mole ${H_2}O$ has a mass of $18.02g$
$10$ moles ${H_2}O$ has a mass of $180.02g$
Total mass of $N{a_2}S{O_4}.10{H_2}O$ $= 142.68g + 180.02g$
Total mass of $N{a_2}S{O_4}.10{H_2}O$ $= 322g$ .
Hence, the correct option is C. $322$ .
The following methods can be used to determine the molecular weight of molecules:
The technology of mass spectrometry is commonly used to determine the mass of tiny compounds. Mono isotopic mass is the term used to describe this.
Mark-Houwink relations are used to determine the weight using the hydrodynamic approach. Because this method necessitates calibration, it's also known as the relative molecular weight determination method.
Static Light Scattering: The Zimm technique is used to determine the molecular weight from the amount of light scattered.

Note :
A substance is something with mass that takes up space. The sum of the total mass in grams of the atoms present in a molecule per mole is the molar mass/molecular weight. The molar mass unit is grams/mole.