Question

What happens when carbon dioxide dissolves in water what is the use of this element

Answer 1

CO2 can exist solvated in water as CO2 but some (most) molecules will actually react with a water molecule to form H2CO3 which, in solution, will dissociate like an acid (in fact, H2CO3 is carbonic acid). So a CO2 solution of CO2 and water will be slightly acidic which is why sparkling water has a salty/sour taste. You can force more CO2 into solution by lowering the temperature and increasing the CO2 pressure (think soda water or coca-cola), and if you relieve the pressure most of it will bubble out of the water back to gaseous CO2 (the fizz in your soda or beer).