Question

Calculate the mass of 10 moles of sodium sulphite $ \text{N}{{\text{a}}_{\text{2}}}\text{S}{{\text{O}}_{\text{3}}} $ .

Answer 1

Hint: The mole is a unit of measurement that is used to express the weight of subatomic and atomic level particles. One mole is defined as equal to $ 6.023\times {{10}^{23}} $ particles. One mole is also equal to the atomic weight of an element and the molecular weight of a compound. We shall multiply the molecular mass of the compound to the number of moles to get the mass.

Complete step by step solution:
The molecular weight of any chemical compound is equal to the sum of the atomic weights of the constituent atoms. As such the molecular weight of sodium sulphite is:
  $ \left[ \left( 23\times 2 \right)+32+\left( 16\times 3 \right) \right]=126.05 $ Gram per mole
 As stated above, one mole is equal to the molecular weight of a compound
Therefore one mole of sodium sulphite = $ 126.05 $ grams per mole
So, the mass of 10 moles of sodium sulphite $ \text{N}{{\text{a}}_{\text{2}}}\text{S}{{\text{O}}_{\text{3}}} $ = $ 126.05\times 10=1260.5 $ grams per mole.

Note:
One mole of any substance is equal to $ 6.023\times {{10}^{23}} $ particles, where the particles can be anything like molecules, atoms, ions and subatomic particles. The number that is equal to one mole is also called the “Avogadro’s Number” in honour of the Italian physicist Amedeo Avogadro. He proposed that equal volumes of all gases contain equal numbers of molecules under similar conditions of temperature and pressure and it was this hypothesis of his that led to the concept of mole. The general conference on weights and measures defined the above number as mole for the system of international units (SI) in effect since May 20, 2019.
The moles was previously defined as the number of atoms determined experimentally to be found in 12 grams of a carbon-12 isotope.