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Chapter 18: Problem 61

Which choice is greener in a chemical process? Explain. (a) Benzene as a solvent or water as a solvent. (b) The reaction temperature is \(500 \mathrm{~K}\), or \(1000 \mathrm{~K}\). (c) Sodium chloride as a by-product or chloroform \(\left(\mathrm{CHCl}_{3}\right)\) as a by-product.

Short Answer

Expert verified
The greener choices in a chemical process are: (a) Using water as a solvent instead of benzene, due to its lower environmental and health impacts. (b) A reaction temperature of 500 K instead of 1000 K, as it consumes less energy and has a lower environmental impact. (c) Sodium chloride as a by-product, which is less harmful to the environment and human health compared to chloroform.

Step by step solution

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1. Solvents: Benzene vs. Water

To determine which choice is greener, we need to consider the solvents' environmental and health impacts. Benzene is an organic solvent and a known carcinogen. It is harmful to the environment and human health. Moreover, it is non-renewable and can be a threat to aquatic life. On the other hand, water is a renewable resource and the most common solvent used in chemical processes. It does not pose any environmental or health hazards. In addition, the use of water can reduce the consumption of organic solvents, which significantly decreases environmental pollution. Therefore, the greener option is to use water as a solvent.
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2. Reaction temperatures: 500 K vs. 1000 K

The reaction temperature can affect the energy consumption of a chemical process and its environmental impact. Higher temperatures generally require more energy, contributing to higher greenhouse gas emissions and a larger carbon footprint. A temperature of 500 K is lower than 1000 K, which means that the chemical process will consume less energy at this temperature. Lower energy consumption is associated with reduced greenhouse gas emissions and lower environmental impact. Therefore, the greener choice in this scenario is the reaction temperature of 500 K.
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3. By-products: Sodium chloride vs. Chloroform

Sodium chloride (commonly known as table salt) is an ionic compound with minimal environmental and health impacts. It is usually non-toxic and readily dissolves in water, making it easy to remove as a by-product in many chemical processes. Chloroform (CHCl₃) is an organic compound that can have negative environmental and health effects. It is a volatile and hazardous substance that can contaminate air, water, and soil. Furthermore, chronic exposure to chloroform can cause liver and kidney damage and increased cancer risk. Considering the environmental and health impacts of the by-products, sodium chloride is the greener option in this case, compared to chloroform.

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