Question

4 HCl + MnO2 ==> MnCl2 + 2 H2O + Cl2

How many grams of MnCl2 are formed when 36.0 grams of water are also formed?
DO we have to calculate mole mass first?

Answer 1

Yes, that's the only way to find the number of mols in 36.0 g H2O then to convert mols MnCl2 to g MnCl2.