Q.Explain the role of green chemistry.

Step 1. State the underlying premise (Section 16.4). The Earth has a natural capacity to absorb waste and pollution; problems arise only once that capacity is exceeded, so green chemistry's role is to keep human chemical activity within that natural capacity.

Step 2. State the core role. Green chemistry promotes innovative chemical technologies that reduce or eliminate the use or generation of hazardous substances across a chemical product's design, manufacture and use.

Step 3. State the economic role. It helps reduce capital expenditure by preventing pollution at its source (cheaper than treating pollution after the fact), and it incorporates pollution-prevention practices directly into how chemicals are manufactured, promoting pollution prevention and industrial ecology.

Step 4. State the two specific environmental benefits named. Green chemistry helps protect the ozone present in the stratosphere (essential for life on Earth) and helps control the greenhouse effect (global warming).

Direct recall of Section 16.4's stated roles of green chemistry.

• Only mentioning pollution reduction and omitting the specific ozone-layer and greenhouse-effect benefits the text names.
• Missing the economic angle (lower capital expenditure from preventing pollution at source, rather than treating it later).