$\begin {array} {1 1} (1)\;reactions\: of\: fused\: NaOH\: with\: C & \quad (2)\;reaction\: of\: NaOH\: with\: sulphur \\ (3)\;heating\: the \: concentrated\: NaOH \: with \: Si & \quad (4)\;reaction \: of\: zinc\: with \: NaOH \end {array}$
