Identify the reactants and the reaction type.

The experiment involves the reaction of graphite (which is a form of carbon, C) with concentrated nitric acid ($\text{HNO}_3$). This is a redox (oxidation-reduction) reaction where carbon is oxidized and nitric acid is reduced.

When carbon reacts with concentrated nitric acid, carbon is oxidized to carbon dioxide ($\text{CO}_2$), and concentrated nitric acid is reduced to nitrogen dioxide ($\text{NO}_2$). Water ($\text{H}_2\text{O}$) is also produced.
The balanced chemical equation for this reaction is:

From the balanced equation, the gaseous products are carbon dioxide ($\text{CO}_2$) and nitrogen dioxide ($\text{NO}_2$).

The procedure states to "Test the gas evolved with (i) a glowing Splint (ii) line water".

• The "line water" test (which is typically lime water, a solution of calcium hydroxide) is a characteristic test for carbon dioxide. Carbon dioxide turns lime water milky due to the formation of insoluble calcium carbonate.
• Nitrogen dioxide ($\text{NO}_2$) is a reddish-brown gas with a pungent odor. It would not give a positive result with the lime water test.

Given that the procedure explicitly mentions a test (lime water) that confirms the presence of carbon dioxide, this is the gas the question is most likely referring to.

The gas produced that would turn lime water milky is carbon dioxide.

The gas produced is carbon dioxide.