Question

The mass of sodium in 11.7g of sodium chloride is

a. 2.3 g

b. 4.6g

c. 6.9 g

d. 7.1 g

Answer 1

The chemical formula of sodium chloride is NaCl.
The molecular mass of NaCl = { 23 + 35.5 }g per mole.
= 58.5 g per mole
As molar mass of Na is 23 g per mole and that of Cl is 35.5 g per mole.
Which means,
1 mole of NaCl weigh = 58.5 g
or
58.5 g of NaCl contain = 1 mole
1 g of NaCl contain = 1/ 58.5 mole
11.7 g of NaCl contain = 11.7 / 58.5 mole
= 0.2 mole
As 1 mole of NaCl contain 1 mole of Na+ ions, therefore
In 11.7 g of NaCl, 0.2 mole of sodium ions are also present.
As mass = moles × molar mass
Mass of sodium = 0.2 ​× 23
= 4.6g
Hence 11.7 g of NaCl contain 4.6 g of sodium