The balanced chemical equation is represented as:
Ba(OH)2·8 H2O + 2 NH4SCN = Ba(SCN)2 + 10 H2O + 2 NH3
To determine the mass of ammonium thiocyanate needed completely react, we use the amount given of the other reactant. Then, convert to moles by the molar mass. And using the relations of the substances in the reaction, we can determine the amount of ammonium thiocyanate.
moles Ba(OH)2·8 H2O = 5.7 g Ba(OH)2·8 H2O ( 1 mol / 315.46 g ) = 0.0181 mol Ba(OH)2·8 H2O
moles NH4SCN = 0.0181 mol Ba(OH)2·8 H2O ( 2 mol NH4SCN / 1 mol Ba(OH)2·8 H2O ) = 0.0361 mol NH4SCN
mass NH4SCN = 0.0361 mol NH4SCN ( 76.122 g / 1 mol ) = 2.75 g NH4SCN
