Hydrogen peroxide is a very famous chemical compound in the people. It is used as a disinfectant in cleaning injuries.
Boiling points of hydrogen peroxide and water are 1500C and 1000C respectively. We know both hydrogen peroxide and water are able to make hydrogen bonds.
Molecular masses of H2O2 and H2O are 34 and 18 respectively. Also hydrogen peroxide molecules have the ability to make more hydrogen bond than water molecules. Due to both greater molecular mass and number of hydrogen bonds, boiling point of hydrogen peroxide is higher than water.
Alkali metals peroxide ( Na2O2, K2O2 ) will react with water and produce
hydrogen peroxide and metal hydroxide.
Na2O2 + H2 → NaOH + H2O2
K2O2 + H2 → KOH + H2O2
Hydrogen peroxide can react in different ways.
Hydrogen peroxide decomposes into water and oxygen gas (O2) when temperature increases or exposing to the sunlight. This reaction can be catalyzed by minute traces of transition metal ions. In the presence of potassium iodide, MnO2 aqueous NaOH will also catalyze the decomposition of H2O2. Also decomposition of H2O2 is an oxidizing-reducing reaction.
But decomposition will slow down when acids are present. ( H2SO4 ).
This reaction is a disproportionation process. Two half reactions (oxidation and reduction) are occurred.
Hydrogen peroxide is reduced to water and other compound is oxidized.
Potassium iodide is oxidized to iodine and hydrogen peroxide is reduced to water. Also in the presence of excess potassium iodide produced iodine combines with iodide ion give red - brown I3-.
Lead sulfide is a black precipitate and reacts with hydrogen peroxide and produce lead sulfate ( PbSO4 ) and water as products. PbSO4 is a white precipitate.
PbCO3 is a white inorganic compound. It is used as a pigment. But due to presence of H2S, PbCO3 is turned to black colour PbS. To take back the white colour, hydrogen peroxide is reacted with lead sulfide.
Ferrous ion ( iron(ii) ) is oxidized to ferric ion ( iron(iii) ) and H2O2 is reduced to water. Green colour of Fe2+ solution is changed to brown - yellow colour due to production of Fe3+.
Sulfurous acid is oxidized to sulfuric acid. So oxidation number of sulfur is increased from +4 to +6. As other product, water is given.
Sulfurous acid is a weak acid and sulfuric acid is a strong acid.