Question

Why test tube get cold when ammonium chloride react with water?

Answer 1

1.as we know pure water is not a good conductor of electricity. But by the       addition of a small amount of acid during electrolysis of water, water could be     decomposed to hydrogen gas and oxgyen gas easily. 
2. n dissolving ammonium chloride (NH4Cl) in water in a test tube, the test tube becomes cold as it takes heat from the surrounding water. Hence, it is an endothermic reaction.