Question

You have a sample of water that contains the organic compound

C7H12ON2 at a concentration of 50
mg/L. The compound can be oxidized by bacteria to form carbon
dioxide, water, and ammonia. How many mg/L of oxygen is needed to
biodegrade the compound? Note: Determine only carbonaceous
demand.

Answer 1

131.4 mg/L of oxygen is needed to biodegrade the organic compound.

Step-by-step explanation:

The chemical reaction will be written as:

`2C_7H_(12)ON_2+23O_2\rightarrow 14CO_2+12H_2O+4NO_2`

Concentration of the organic compound = 50 mg/L

This means that 50 milligrams of organic compound in present in 1 L of the solution.

50 mg = 0.050 g

1 mg = 0.001 g

Moles of organic compound =
`(0.050 g)/(140 g/mol)=0.0003571 mol`

According to reaction, 2 moles of organic compound reacts with 23 moles of oxygen gas.

Then 0.0003571 moles of an organic compound will react with:

`(23)/(2)* 0.0003571 mol=0.004107 mol` oxygen gas.

Mass of 0.004107 moles of oxygen gas:

0.004107 mol × 32 g/mol = 0.1314 g = 131.4 mg

131.4 mg/L of oxygen is needed to biodegrade the organic compound.