In this question, we have the following reaction:
CuSO4 + Zn -> Cu + ZnSO4, as the question already says, this is a single replacement reaction
We have:
145.0 grams of Cu (Copper)
We have to find out how much Zn we had at the beginning of the reaction
First thing we need to do is find out how many moles of Copper we have, we will do it by using its molar mass, 63.55g/mol, and the given mass in the question, 145g
63.55g = 1 mol
145g = x moles
x = 2.28 moles of Copper in 145 grams
Now, according to the molar ratio, if we have 1 mol of Zn, we will produce 1 mol of Cu, therefore if we have 2.28 moles of Cu, we will have 2.28 moles of Zinc as well
Now we will find the mass of Zinc, using the number of moles, 2.28 moles and its molar mass, 65.38g/mol
65.38g = 1 mol
x grams = 2.28 moles
x = 149.1 grams of Zinc was used