Question

Which of the tollowing practices involve green chemistry? (i) Substitute CFCs by environmental friendly HFCs and other compounds. (ii) Replace halogenated solvent by liquid \(\mathrm{CO}_{2}\) for drycleaning. (iii) Use of \(\mathrm{H}_{2} \mathrm{O}_{2}\) for bleaching instead of \(\mathrm{Cl}_{2}\). (iv) Making disposable eating utensils and storage jars of plastics. (a) (i) and (ii) (b) (ii) and (iv) (c) (iii) and (iv) (d) (i), (ii) and (iii)

Short answer

Practices (i), (ii), and (iii) involve green chemistry, so the correct answer is (d) (i), (ii) and (iii).

Step-by-step solution

Understanding Green Chemistry

Green chemistry aims to reduce or eliminate the use and generation of hazardous substances in the design, manufacture, and application of chemical products. It focuses on sustainability and environmental safety.

Evaluating Option (i)

Substituting chlorofluorocarbons (CFCs) with hydrofluorocarbons (HFCs) and other compounds is an environmentally friendly practice. CFCs deplete the ozone layer, while HFCs are less harmful.

Evaluating Option (ii)

Replacing halogenated solvents with liquid carbon dioxide (CO2) for dry cleaning is a green chemistry practice. Liquid CO2 is non-toxic, non-flammable, and can be recycled, minimizing environmental impact.

Evaluating Option (iii)

Using hydrogen peroxide (H2O2) for bleaching instead of chlorine (Cl2) reduces the production of harmful chlorinated byproducts. This is a green chemistry approach.

Evaluating Option (iv)

Making disposable utensils and storage jars of plastics is not generally considered green chemistry, as it promotes single-use items and contributes to plastic pollution.

Key concepts

Environmentally Friendly Chemical Practices

Understanding environmentally friendly chemical practices means considering how every aspect of a chemical's life cycle can be optimized to minimize negative environmental impacts. These practices aim to design safer products and processes that reduce the amount and toxicity of waste and emissions.

For instance, the substitution of harmful chlorofluorocarbons (CFCs) with less damaging hydrofluorocarbons (HFCs) represents a push toward safer alternatives. As mentioned in the exercise solution, CFCs have a known detrimental effect on the ozone layer, which protects life on Earth from harmful ultraviolet radiation.

Advantages of Using HFCs Over CFCs

• Reduced ozone depletion potential
• Lower global warming impact compared to some other gases
• May be used as transitional substitutes while more sustainable options are developed

Sustainable Chemical Alternatives

Incorporating sustainable chemical alternatives into industrial and domestic applications reflects a critical aspect of green chemistry. These alternatives are chosen for their eco-friendliness and effectiveness at performing a specific function. As per the step-by-step solution, using liquid \(\mathrm{CO}_2\) instead of traditional halogenated solvents in dry cleaning processes serves as an excellent illustration. This switch not only mitigates the release of volatile organic compounds into the atmosphere but also capitalizes on the recycling potential of \(\mathrm{CO}_2\).

Benefits of Liquid \(\mathrm{CO}_2\) in Dry Cleaning

• Minimizes toxic emissions and exposure
• Supports a closed-loop system where \(\mathrm{CO}_2\) can be reused
• Non-flammable and safer for workers

Reduction of Hazardous Substances

Reducing hazardous substances is foundational to green chemistry. This concept aims to lower human and environmental exposure to dangerous chemicals. For example, the exercise solution indicates that using hydrogen peroxide (\(\mathrm{H}_2\mathrm{O}_2\)) for bleaching clothes rather than chlorine (\(\mathrm{Cl}_2\)) reduces the risk of creating harmful chlorinated byproducts.

The impact of such changes in industrial practices translates into broader environmental health benefits, including:

Environmental and Health Benefits

• Decreased risk of water and soil pollution from toxic byproducts
• Improved safety for workers handling the chemicals
• Better overall air quality due to reduced emissions