How many grams of H3BO3 forms when 28.16 grams B2H6 react with excess water?
Do you have an equation. Balance it first.
mols B2H6 = grams/molar mass
Use the coefficients in the balanced equation to convert mols B2H6 to mols H3PO3.
Now convert mols H3BO3 to grams. g = mols x molar mass.