Question

0.27f of aluminium reacts with 2.4 of bromine. How many moles of bromine are there in 2.4g of bromine? (Br=79.9)

Answer 1

Moles = mass / molar mass = 2.4 g / 79.9 g·mol⁻¹ = 0.0300 mol (≈3.00 × 10⁻² mol) of bromine atoms.

Note: If you mean molecular bromine (Br2), its molar mass is 159.8 g·mol⁻¹, so n(Br2) = 2.4 / 159.8 ≈ 0.0150 mol.