In the gaseous state, chlorine exists as a diatomic molecule Cl2 (Molar mass = 70.9 g/mol). Calculate the number of moles of chlorine present in 140 g of chlorine gas. Express the quantity in moles to three significant figures.

Cl is stable as a diatomic molecule where the 2 Cl atoms are held together by a covalent bond

molar mass of the diatomic molecule is 70.9 g/mol

therefore 70.9 g of Cl₂ is - 1 mol

then 140 g of Cl₂ is - 1/70.9 x 140 = 1.97 mol

there are 1.97 mol of Cl₂ present

1 mole = 70.9

X mole = 140

X=1.9746 moles

X = 1.98 when rounded to 3 significant figures.