According to the following reaction the minimum quantity in gm of ${\mathrm{H}}_2\mathrm{S}$ needed to precipitate 63.5 gm of ${\mathrm{Cu}}^{2+}$ion will be nearly:

${\mathrm{Cu}}^{+2}+{\mathrm{H}}_2\mathrm{S}⟶\mathrm{CuS}+2{\mathrm{H}}^{+}$