HELLO LAKSHAY,
the below thing happens as zinc is more reactive than copper
understand this reaction
CuSO4 -------------> Cu2+ + SO4^2-
since excess of zinc is added then
CuSO4 + Zn ---------------> ZnSO4 + Cu
=> 1 mol of zinc === 1 mol of ZnSO4
so concentration of Cu = 1 mol
THANK YOU