Aliphatic amines with nitrous acid give a quantitative yield of nitrogen gas and is the basis of Van slyke determination of amino nitrogen. The volume of nitrogen liberated at STP (in ml) when 0.01 mole of proline react with excess nitrous acid.   

The reaction between an aliphatic amine and nitrous acid produces nitrogen gas as shown below:

RNH₂ + HNO₂ → RNO + H₂O + N₂

The reaction is a redox reaction, where nitrous acid is the oxidizing agent and the amine is the reducing agent. The nitrogen gas produced can be used to determine the amount of amino nitrogen present in a sample, a method known as the Van Slyke determination.

To calculate the volume of nitrogen gas liberated at STP when 0.01 mole of proline reacts with excess nitrous acid, we first need to balance the equation for the reaction:

C₅H₉NO₂ + HNO₂ → C₅H₈NO + H₂O + N₂

From the balanced equation, we can see that one mole of proline reacts with one mole of nitrous acid to produce one mole of nitrogen gas. Therefore, 0.01 mole of proline will produce 0.01 mole of nitrogen gas.

At STP (standard temperature and pressure), one mole of gas occupies 22.4 L. Therefore, 0.01 mole of gas will occupy:

0.01 mole × 22.4 L/mole = 0.224 L or 224 mL

So the volume of nitrogen gas liberated at STP when 0.01 mole of proline reacts with excess nitrous acid is 224 mL.