Question

a scientist uses 52 grams of Na2SO4 for a chemical reaction.
how many moles of Na atoms does the compound contain?

Answer 1

Answer- The above question is from the chapter 'Some Basic Concepts of Chemistry'.

Concept used: 1) Number of moles = $\frac{Given \: mass}{Molar \: mass}$

Given question: A scientist uses 52 grams of Na₂SO₄ for a chemical reaction. How many moles of Na atoms does the compound contain?

Answer: Given mass of Na₂SO₄ = 52 grams

Molar mass of Na₂SO₄ = 2 [Na] + 1 [S] + 4 [O] = 2 [23] + 32 + 4 [16] = 142 grams

Number of moles of Na₂SO₄ = $\frac{Given \: mass}{Molar \: mass}$

                                                 = $\frac{52}{142}$

                                                 = $\frac{26}{71}$

In 1 mole of Na₂SO₄, there are 2 moles of Na.

In $\frac{26}{71}$ moles of Na₂SO₄, number of moles of Na

= 2 × $\frac{26}{71}$

= $\frac{52}{71}$

= 0.732 moles

∴ Required number of moles of Na atoms in 52 grams of Na₂SO₄ is 0.732 moles.