Explain why ammonia gas cannot be dried by passing h2so4?

Ammonia is a base, and sulfuric acid is well, an acid. When an acid and base react, they form a salt. In the case of ammonia and sulfuric acid, they will react to form ammonium sulphate.

It is a solid and will dissolve in water. One would then need to separate it from the sulfuric acid that remains and then treat it with sodium hydroxide to get ammonia again.But you will likely use aqueous sodium hydroxide, which means that you have to find a way to dry the product as a result. Back to square one.

Hope this helps

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.