What mass of hbr (in g) would you need to dissolve a 3.4 - g pure iron bar on a padlock?

Given:

Mass of pure iron (Fe) = 3.4 g

To determine:

Mass of HBr needed to dissolve the above iron

Explanation:

Reaction between HBr and Fe is

Fe + 2HBr → FeBr₂ + H₂

Based on the reaction stoichiometry-

1 mole of Fe reacts with 2 moles of HBr

# moles of Fe = mass of Fe/atomic mass of Fe = 3.4/56 g. mol⁻¹ = 0.0607 moles

Therefore # moles of HBr = 2*0.0607 = 0.1214 moles

Molar mass of HBr = 81 g/mole

Mass of HBr = 0.1214 moles * 81 g/mole = 9.83 g

Ans: Mass of HBR required is 9.83 g