### Theory:

Combustibility:

Carbon dioxide is neither combustible gas nor supports for combustion.

Reaction with metals:

Lighter metals such as sodium, potassium and calcium, combine with $$CO_2$$ to form corresponding carbonates, while magnesium gives its oxide and carbon.

Example:

$\begin{array}{l}4\mathit{Na}+3{\mathit{CO}}_{2}\stackrel{}{⟶}\phantom{\rule{0.147em}{0ex}}2{\mathit{Na}}_{2}{\mathit{CO}}_{3}+C\\ \mathit{Sodium}\phantom{\rule{2.793em}{0ex}}\mathit{Sodium}\phantom{\rule{0.147em}{0ex}}\mathit{carbonate}\\ \\ \mathit{2Mg}+{\mathit{CO}}_{2}\stackrel{}{⟶}\phantom{\rule{0.147em}{0ex}}2\mathit{MgO}+C\\ \mathit{Magnesium}\phantom{\rule{1.617em}{0ex}}\mathit{Magnesium}\phantom{\rule{0.147em}{0ex}}\mathit{oxide}\end{array}$

Reaction with sodium hydroxide (alkali):

When an acid reacts with a base, it forms salt and water. Carbon dioxide is an acidic oxide, which reacts with sodium hydroxide (a base) to form salt and water.

$\mathit{Acid}+\mathit{Base}\phantom{\rule{0.147em}{0ex}}\stackrel{}{⟶}\phantom{\rule{0.147em}{0ex}}\mathit{Salt}+\mathit{Water}$

$\begin{array}{l}{\mathit{CO}}_{2}+2\mathit{NaOH}\phantom{\rule{0.147em}{0ex}}\stackrel{}{⟶}{\phantom{\rule{0.147em}{0ex}}\mathit{Na}}_{2}{\mathit{CO}}_{3}+{H}_{2}O\\ \phantom{\rule{2.646em}{0ex}}\mathit{Sodium}\phantom{\rule{2.499em}{0ex}}\mathit{Sodium}\phantom{\rule{1.176em}{0ex}}\\ \phantom{\rule{2.646em}{0ex}}\mathit{hydroxide}\phantom{\rule{1.764em}{0ex}}\mathit{carbonate}\phantom{\rule{0.294em}{0ex}}\end{array}$

Reaction with lime water (calcium hydroxide or $$Ca(OH)_2$$):

When carbon dioxide slightly passes through lime water, it forms a white precipitate (milky appearance milky) of calcium carbonate.

$\begin{array}{l}{\mathit{Ca}\left(\mathit{OH}\right)}_{2}+{\mathit{CO}}_{2}\stackrel{}{⟶}{\phantom{\rule{0.147em}{0ex}}\mathit{CaCO}}_{3}+{H}_{2}O\\ \mathit{Calcium}\phantom{\rule{5.145em}{0ex}}\mathit{Calcium}\\ \mathit{hydroxide}\phantom{\rule{4.704em}{0ex}}\mathit{carbonate}\phantom{\rule{2.793em}{0ex}}\end{array}$

When adding an excess amount of carbon dioxide through lime water, it forms a precipitate, and the precipitate disappears due to the formation of soluble calcium hydrogen carbonate ($$Ca(HCO_3)_2$$).