Question

2litres of N2and 2litres of H2 on completion of reaction what is the volume of NH3

Answer 1

balanced reaction is 
N2 + 3 H2 ==>  2 NH3 , so 1 litre of N2 reacts with 3 litres of H2. But there are only 2 litres of H2 available, so H2 is limiting reagent. I hope you know what is a limiting reagent. Now 3 litres of H2 reacts to give 2 litres of NH3. So 1 litres of available H2 reacts to give  2/3 litres of ammonia. And 2 litres of H2 reacts to give 4/3 litres of NH3. I hope this helps