#"Moles of calcium oxide"# #=# #(1.5*g)/(56.08*g*mol^-1)=??*"moles"#.
I think your original question would have asked you the concentration of the solution with respect to calcium; and maybe its #pH# if an initial volume were specified.
#"Concentration"# #=# #(1.5*g)/(56.08*g*mol^-1)xx1/("Volume (L)")# #=# #??*mol*L^-1#.
#pH=-log_10{2xx(1.5*g)/(56.08*g*mol^-1)xx1/("Volume (L)")}=??#
Note that #"calcium oxide"# dissolves in water according to the following reaction:
#CaO(s) + H_2O(l) rarr Ca(OH)_2(aq)#