Q.a. Ozone is used as bleaching agent. Explain.
Step 1. Ozone is thermodynamically unstable relative to ordinary dioxygen, and readily decomposes: O3 -> O2 + O, releasing a highly reactive single oxygen atom, sometimes called 'nascent' oxygen.
Step 2. This nascent oxygen atom is a powerful oxidising species, and reacts with the chromophores (colour-causing chemical groups) in coloured organic matter, chemically altering them into colourless products: coloured organic matter + [O] -> colourless organic matter.
Step 3. Because this bleaching mechanism depends only on ozone's own decomposition and not on any reaction with water, ozone bleaches effectively even in the complete absence of moisture -- which is why it is specifically described as a 'dry bleach', in contrast to chlorine, which needs moisture present to bleach (section 7.11.1).
Ozone acts as a bleaching agent because it decomposes to liberate reactive nascent oxygen (O3 -> O2 + O), which oxidises coloured organic matter into colourless products; since this requires no moisture, ozone is known as a dry bleach.
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