c
(c) [ Molecular weight of \(CuS{O_4}.5{H_2}O\) \( = 63.5 + 32 + 64 + 90\)\( = 249.5\)] \(6 \times {10^{23}}\)molecules has weight \( = 249.5\,gm\) \(1 \times {10^{22}}\) molecules has weight \( = \frac{{249.5 \times 1 \times {{10}^{22}}}}{{6 \times {{10}^{23}}}}\) \( = 41.58 \times {10^{ - 1}}\) \( = 4.158\)