Question

Find the theoretical oxygen demand for the

Answer 1

Answer:

a) 213.3 mg/L

b) 62.61 mg/L

c) 0.0225 mg/L

Explanation:

Theoretical oxygen demand (ThOD)is essentially the amount of oxygen required for the complete degradation of a given compound into the final oxidized products

a) Given:

Concentration of acetic acid,$[CH3COOH]$ = 200 mg/L

$CH3COOH + 2O2 \rightarrow 2CO2 + 2H2O$

$ThOD = \frac{mass\ O2}{mass\ CH3COOH} * conc. CH3COOH$

Based on the reaction stoichiometry:

mass of $CH3COOH$ = 60 g

mass of $O2$= 2(32) = 64 g

$ThOD = \frac{64 g}{60 g} * 200mg/L = 213.3 mg/L$

b) Given:

Concentration of ethanol, $[C2H5OH]$ = 30 mg/L

$C2H5OH + 3O2 \rightarrow 2CO2 + 3H2O$

$ThOD = \frac{mass\ O2}{mass\ C2H5OH} * conc. C2H5OH$

Based on the reaction stoichiometry:

mass of $C2H5OH$ = 46 g

mass of $O2$= 3(32) = 96 g

$ThOD = \frac{96 g}{46 g} * 30mg/L = 62.61 mg/L$

c) Given:

Concentration of sucrose, $[C12H22O11]$ = 50 mg/L

$C12H22O11 + 12O2 \rightarrow 12CO2 + 11H2O$

$ThOD = \frac{mass\ O2}{mass\ C22H22O11} * conc. C12H22O11$

Based on the reaction stoichiometry:

mass of $C12H22O11$ = 342 g

mass of $O2$= 12(32) = 384 g

$ThOD = \frac{384 g}{342 g} * 50mg/L = 0.0225 mg/L$