From a hydrogen peroxide (diluted in water) a sample of 1.00 g is removed, acidifing it with H2SO4 and then titrated with a solution of 0.20 M of KMnO4, requiring 17.6 mL of KMnOH. What is the percentage of H2O2 contained in the bottle?
5H2O2 + 2KMnO4 + 3H2SO4 = 5O2 + 2MnSO4 + K2SO4 + 8H2O
millimols KMnO4 used = mL x M = 17.6 mL x 0.2 M = ?
Convert to mmols H2O2 = ? mmols KMnO4 x (5 mols H2O2/2 mols KMnO4) = ??
Change mmols H2O2 to mols (divide by 1000)
grams H2O2 = mols H2O2 x molar mass H2O2 = ?
%H2O2 = (grams H2O2/1.00 g sample)100 = ?
NOTE: This is the %H2O2 in the diluted sample. It is not the %H2O2 in the bottle, before dilution, and without know the dilution factor one may not calculate how much is in the bottle of H2O2.
To find the percentage of hydrogen peroxide (H2O2) in the bottle, we need to calculate the amount of H2O2 reacted in the titration.
1. First, let's calculate the number of moles of KMnO4 used in the titration. We know the volume of KMnO4 solution used (17.6 mL) and its concentration (0.20 M).
Moles of KMnO4 = Volume (in L) × Concentration
Moles of KMnO4 = 17.6 mL × (1 L / 1000 mL) × 0.20 M
Moles of KMnO4 = 0.00352 mol
2. The balanced chemical equation for the reaction between H2O2 and KMnO4 is:
5 H2O2 + 2 KMnO4 + 3 H2SO4 → 5 O2 + 2 MnSO4 + 3 H2O + 3 K2SO4
In this equation, the ratio between H2O2 and KMnO4 is 5:2. So, the moles of H2O2 reacted can be calculated as follows:
Moles of H2O2 = (Moles of KMnO4) × (5/2)
Moles of H2O2 = 0.00352 mol × (5/2)
Moles of H2O2 = 0.0088 mol
3. Now, let's calculate the molar mass of H2O2. Hydrogen (H) has a molar mass of 1 g/mol, and oxygen (O) has a molar mass of 16 g/mol.
Molar mass of H2O2 = (2 × Molar mass of H) + (2 × Molar mass of O)
Molar mass of H2O2 = (2 × 1 g/mol) + (2 × 16 g/mol)
Molar mass of H2O2 = 34 g/mol
4. To find the mass of H2O2 in the sample, we can use the following equation:
Mass of H2O2 = Moles of H2O2 × Molar mass of H2O2
Mass of H2O2 = 0.0088 mol × 34 g/mol
Mass of H2O2 = 0.2992 g
5. Finally, we can calculate the percentage of H2O2 in the bottle using the following equation:
Percentage of H2O2 = (Mass of H2O2 / Mass of the sample) × 100
Percentage of H2O2 = (0.2992 g / 1.00 g) × 100
Percentage of H2O2 = 29.92%
Therefore, the bottle contains approximately 29.92% hydrogen peroxide.