Fe2o3(s) + 3co(
g. → 2fe(s) +3co2(
g. how many grams of iron can be produced from 1.00 kg fe2o3?

The answer is, 699g 
The idea here is that you need to use the mole ratio tha  exists between ferric oxide, Fe2O3, and iron metal,   Fe, to determine how many moles  of the latter will be produced when all the given mass of the ferric oxide reacts...

Answer is: mass of hydrochloric acid is 4,08 grams.chemical reaction: 2hcl + mg(oh)₂ → mgcl₂ + 2h₂o.m(mg(oh)₂) = 3,26 g.n(mg(oh)₂) = m(mg(oh)₂)  ÷ m(mg(oh)₂).n(mg(oh)₂) = 3,26 g  ÷ 58,32 g/mol.n(mg(oh)₂) = 0,056 mol.from chemical reaction: n(mg(oh)₂) : n(hcl) = 1 : 2.n(hcl) = 2  · 0,056 mol = 0,112 mol.m(hcl) = 0,112 mol  · 36,45 g/mol.m(hcl) = 4,08 g.