Fe + CuSO₄ ----> FeSO₄ + Cu
According to that equation, 1 mol of Fe will react with 1 mol of CuSO₄ to give 1 mol of FeSO₄ and 1 mol of Cu.
The first step to solve the problem is to find the number of moles of Fe that we have in 3.8 g of it. To do that we have to use the molar mass.
molar mass of Fe = 55.85 g/mol
number of moles of Fe = mass of Fe/molar mass of Fe
number of moles of Fe = 3.8 g /(55.85 g/mol)
number of moles of Fe = 0.068 moles of Fe
Once that we know that 3.8 grams of Fe represents 0.068 moles of Fe, we can find the number of moles of Cu produced by those moles (since Fe reacts with excess of CuSO₄). According to the coefficients of the equation of the reaction:
number of moles of Cu produced = 0.068 moles of Fe * 1 mol of Cu/(1 mol of Fe)
number of moles of Cu produced = 0.068 moles of Cu
Finally we can convert those moles of Cu produced into grams using the molar mass of Cu.
molar mass of Cu = 63.55 g/mol
mass of Cu produced = 0.068 moles * 63.55 g/mol
mass of Cu produced = 4.32 g
Answer: b) 4.3 g of Cu are produced.