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100 ml of a sample of water requires 1.9...

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.

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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` Oxygen
`1.96 xx 10^(-3) gK_(2)Cr_(2)O_(7) rarr (8xx1.96 xx10^(-3))/49=0.32` mg
Chemical oxygen demand of the given 100 ml sample of water = `(0.32)/(0.1)=3.2` ppm
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