10 ml of `H_2` contain 2000 molecules under certain temperature and pressure. Calculate the number of molecules of oxygen whose volume is 150 ml at same temperature and pressure.

Explanation

According to Avogadro's law at same conditions of temperature and pressure equal volumes of all gases contain equal number of molecules.
10 ml of `O_2` contain2000 molecules
150 ml of `O_2` contain `2000/10xx150 = 30,000` molecules