(a) When concentrated sulfuric acid is added to oxalic acid, it acts as a dehydrating agent and removes water from the oxalic acid, producing carbon monoxide, carbon dioxide, and water: $$ \begin{aligned} \text{COOH}-\text{COOH} + \text{H}_2\text{SO}_4 \xrightarrow{\text{conc.}} \text{CO} + \text{CO}_2 + \text{H}_2\text{SO}_4 \cdot \text{H}_2\text{O} \end{aligned} $$ (b) When an excess of caustic soda (NaOH) is added to aluminum sulfate solution, aluminum hydroxide is initially formed as a white precipitate, which then dissolves in excess NaOH to form soluble sodium aluminate: $$ \begin{aligned} \text{Al}_2(\text{SO}_4)_3 + 6\text{NaOH} &\rightarrow 2\text{Al}(\text{OH})_3 \downarrow + 3\text{Na}_2\text{SO}_4 \\ \text{Al}(\text{OH})_3 + \text{NaOH} &\rightarrow \text{NaAlO}_2 + 2\text{H}_2\text{O} \end{aligned} $$ (c) When alcohol reacts with thionyl chloride, it produces alkyl chloride, sulfur dioxide gas, and hydrogen chloride gas: $$ \begin{aligned} \text{R}-\text{OH} + \text{SOCl}_2 &\rightarrow \text{R}-\text{Cl} + \text{SO}_2 \uparrow + \text{HCl} \uparrow \end{aligned} $$ (d) When dry chlorine gas reacts with slaked lime at 40°C, it produces bleaching powder: $$ \begin{aligned} \text{Ca}(\text{OH})_2 + \text{Cl}_2 &\xrightarrow{40^\circ\text{C}} \text{CaOCl}_2 + \text{H}_2\text{O} \end{aligned} $$ (e) When carbon is added to hot and concentrated sulfuric acid, it is oxidized to carbon dioxide, while the acid is reduced to sulfur dioxide: $$ \begin{aligned} \text{C} + 2\text{H}_2\text{SO}_4 &\rightarrow \text{CO}_2 + 2\text{SO}_2 + 2\text{H}_2\text{O} \end{aligned} $$