Identify the correct statements from the following: i. In the presence of UV light, ( CF ₂ Cl ₂(g) ) gives chlorine free radicals which will react with ( O ₃(g) ) to form ( O ₂(g) ). ii. Drinking water with (10 ppm ) fluoride is better than drinking water with (1 ppm ) fluoride. iii. The maximum permissible concentration of lead in drinking water is (50 ppb ).

Step-by-step solution

Statement (i) and (iii) are correct statements whereas statement (ii) is incorrect. Its correct explanation is as follows: The drinking water with (1 ppm ) fluoride is better than (10 ppm ) fluoride. The EPA has set maximum allowable concentration of fluorine in water at (2 ppm ) to prevent enamel fluorosis and (4 ppm ) to prevent skeletal fluorosis.