Question

You are given the following decomposition reaction of ammonia
NH3 ---> H2 + N3 unbalanced

When you decompose 12.0g of NH3you produce 1.87 g of H2 Calculate the percent yield of H2

Answer 1

I believe you goofed on the formula (in addition to not balancing it).
2NH3 ==> 3H2 + N2
mols12.0g NH3 = grams/molar mass = ?
Convert mols NH3 to mols H2 using the coefficients in the balanced equation.
Convert mols H2 to grams. g = mols x molasr mass. This is the theoretical yield. The actual yield according to the problem is 1.87g.
%yield = (actual yield/theor yield)*100 = ?

Answer 2

87.6%