100 ml of a sample of water requires 1.96 mg of potassium dichromate in the presence of 50% H_2SO_4 for the oxidation of dissolved organic matter in it. Calculate the chemical oxygen demand.

100 ml of a sample of water requires 1.96 mg of potassium dichromate i

1.	100 ml of a sample of water requires 1.96 mg of potassium dichromate in the presence of 50% H_2SO_4 for the oxidation of dissolved organic matter in it. Calculate the chemical oxygen demand.
Answer» Solution :One gram equivalent of any OXIDANT can give, one equivalent weight of OXYGEN (8 G) `49 g K_2Cr_2O_7 to 8g " Oxygen"` ` 1.96 xx 10^(-3) g K_2Cr_2O_7 to (8 xx 1.96 xx 10^(-3))/(49)=0.32 mg ` Chemical oxygen demand of the given 100 ml SAMPLE of water `=(0.32)/(0.1) = 3.2 ppm`