Answer
a) $290.8\ g/mol$
b) $249.7\ g/mol$
Work Step by Step
Atomic weights: $Ni: 58.693u,\ O: 15.999u,\ S: 32.06u,\ N: 14.007u,\ C: 12.011u,\ Cu: 63.546u,\ H:1.008u$
$H_2O$: 2 H + 1 O: $2\times1.008+15.999=18.01\ g/mol$
a) $Ni(NO_3)_2\dot{}6\ H_2O$: 1 Ni + 2 N + 6 O + 6 $H_2O$:
$58.693+2\times14.007+6\times15.999+6\times18.01=290.8\ g/mol$
b) $CuSO_4\dot{}5\ H_2O$: 1 Cu + 1 S + 4 O + 6 $H_2O$:
$63.546+32.06+4\times15.999+5\times18.01=249.7\ g/mol$
