Question

100 ml of a sample of water requires 1.96 mg of potassium dichromate in the presence of `50% H_(2)SO_(4)` for the oxidation of dissolved oxygen demand.

Answer 1

One gram equivalent of any oxidant can give, one equivalent weight of oxygen (8 g)
`49 g K_(2) Cr_(2)O_(7) rarr 8g O_(2)`
`1.96 K_(2) Cr_(2)O_(7) rarr ?`
`=(8xx1.96)/(49)=0.32 mg`
Chemical oxygen demand of the given 100 ml
sample of water `=0.32/0.1=3.2` ppm