Answer:
71.1
Step-by-step explanation:
1 mol Fe = 10.4 g/55.85 g/mol = 0.186
1 mol AgNo3 = 28.4 g/169.87 g/mol = 0.178 mol AgNo3
then since Ag:Fe is 1:3, AgNo3 is the limiting reactant
So now
0.178 moles * 1/3 * 241.83 g/mol Fe(NO3)3 = 14.35 g Fe(NO3)3
Excess reactant: 0.178 moes AgNO3 * 1/3 = 0.059
0.186 - 0.059 = 0.127 moles Fe * 55.85 g/mol Fe = 7.1 g Fe excess