Hydrogen peroxide (H2O2), which can oxidize a variety of inorganic and organic compounds under mild — Organic Chemistry Chemistry Question

Hydrogen peroxide (H₂O₂), which can oxidize a variety of inorganic and organic compounds under mild reaction conditions, is widely used in industry, particularly the chemical industry. Because water is the only degradation product of H₂O₂, it is an environmentally friendly oxidant. The adduct of hydrogen peroxide with urea through hydrogen bonding is considered to be a useful “solid form” of hydrogen peroxide (urea-hydrogen peroxide: UHP). UHP is an inexpensive and safe oxidant similar to aqueous hydrogen peroxide. Since UHP is a stable solid, it is more convenient to use than aqueous hydrogen peroxide.

In this experiment, you will prepare UHP by mixing urea and aqueous hydrogen peroxide. UHP will be obtained as white needle crystals via slow evaporation. The hydrogen peroxide content will be determined by redox titration using potassium permanganate.

Chemicals
* hydrogen peroxide, 30%
* manganese dioxide
* potassium permanganate (after standardization), c = 0.02 mol dm^-3
* urea

Apparatuses and glassware
* test solution (prepare as described above)
* beaker (100 cm₃)
* burette (25 cm₃)
* conical flask (300 cm₃)
* Erlenmeyer flask (10 cm₃)
* filter paper
* graduated pipette
* test tube
* volumetric flask (100 cm₃)
* volumetric pipette (10 cm₃)
* water bath on a heating plate
* watch glass (preferably ca. 20 cm in diameter)

Procedure
1. Pipette about 3.4 cm₃ of 30% hydrogen peroxide into a 10 cm₃ Erlenmeyer flask using a volumetric pipette and add 1.2 g of urea (hydrogen peroxide : urea = 3 : 2 mole ratio). Heat a water bath to 60 °C (taking care to regulate the temperature to avoid hydrolysis of urea). Place the Erlenmeyer flask containing the mixture in the water bath and heat it for a few minutes to yield a clear, colorless solution. Transfer the solution to a watch glass for slow evaporation.
2. Needle-like crystals will gradually develop from the solution. After the crystallization is completed, place the needle-like crystals on a filter paper to remove the moisture. Weigh the crystals.
3. Place about 0.1 g of the crystals in a test tube and add water. Put a trace of manganese dioxide in the test tube to confirm the formation of an oxygen bubble.
4. Accurately weigh approximately 0.62 g of the crystals and transfer them to a 100 cm₃ beaker. Add 50 cm₃ of water to dissolve the crystals. Transfer the solution to a 100 cm₃ volumetric flask and dilute it with water to the 100 cm₃ mark. Pipette 10 cm₃ of the solution into a 300 cm₃ conical flask. Add 200 cm₃ of water and 20 cm₃ of diluted sulfuric acid (10%).
5. Titrate the solution with standard 0.02 mol dm–3 potassium permanganate until a faint pink color persists for 15 s. Be sure to add the standard 0.02 mol dm–3 potassium permanganate slowly to prevent the formation of manganese dioxide. As a blank test, the same titration should be done without the crystals.