At standard pressure, hydrogen peroxide, H2O2, melts at -0.4°C. boils at 151°C, and is very soluble in water. A bottle of aqueous hydrogen peroxide, H2O(aq), purchased from a pharmacy has a pressure-releasing cap. Aqueous hydrogen peroxide decomposes at room temperature, as represented by the balanced equation below.

2H2O2(aq)==> 2H2O(l) + O2(g) + 196.0 kJ

State. in terms of both melting point and boiling point, why H2O2 is a liquid at room temperature.
State evidence that indicates the decomposition of H2O2(aq) is exothermic.
Explain why a hydrogen peroxide bottle needs a pressure-releasing cap.



Answer :

The room temperature is usually 20℃. And it it higher than melting point and lower than boiling point. So it is liquid at room temperature. The energy is at the right of the equation and with the positive sign which represents this is energy releasing(exothermic). Due to it can decomposes at RT and will create gas, this will increase the pressure inside the bottle. So it need pressure-releasing cap.