GATE Civil Engineering (CE) 2020 Shift 2 Solved Paper

Question : 43 of 65

Marks: +1, -0

A sample of water contains an organic compound

{C}_{8} {H}_{16} {O}_{8}

at a concentration of

10^{-3}

{mol} {/}

litre. Given that the atomic weight of

{C}=12 {g} {/} {mol}, {H}=1 {g} {/} {mol}

, and

{O}=16 {g} {/}{mol}

, the theoretical oxygen demand of water (in

{g}

{O}_{2}

per litre, round off to two decimal places), is

Solution:

{C}_{8} {H}_{16} {O}_{8}+8 {O}_{2} → 8 {CO}_{2}+8 {H}_{2} {O}

1 mole of

{C}_{8} {H}_{16} {O}_{8}

require 8 mole of

{O}_{2}

∴ 10^{-3}

mole/I require

=8 × 10^{-3}

mole/I

8 × 10^{-3}=\;{x}/{32} ⇒ x=0.256 {g} {/}\l

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