# Question #5ae19

##### 1 Answer
Mar 12, 2015

The COD is 348 mg/L.

The chemical oxygen demand (COD) is number of milligrams of oxygen needed to completely oxidize the solutes in a litre of water.

Step 1. Write the balanced equation for the combustion of formic acid.

2HCOOH + O₂ → 2CO₂ + 2H₂O

Step 2. Calculate the mass of HCOOH in 1 L of water.

$\text{1 L H"_2"O" × "0.100 g HCOOH"/("0.100 L H"_2"O") = "1.00 g HCOOH}$

Step 3. Calculate the mass of O₂.

${\text{1.00 g HCOOH" × "1 mol HCOOH"/"46.03 g HCOOH" × ("1 mol O"_2)/"2 mol HCOOH" × ("32.00 g O"_2)/("1 mol O"_2) = "0.348 g O"_2 = "348 mg O}}_{2}$

The COD of this solution is 348 mg/L.