green chem & tech short answers

explain the main principles of green chemistry and their importance

Waste prevention; It’s easier to prevent waste and by-product rather than clean it up once it’s formed

Atom economy; It designs chemical processes to eliminate waste before it’s created by measuring how much reactant goes into the product

Safer chemicals, auxiliaries, and solvents; It helps by preventing hazardous waste, lowering human exposure risks, and eliminates environmental/ecological damage

Design for degradation; It prevents chemical products from accumulating in the environment

12 principles of green chemistry

1. Waste prevention

2. Design for degradation

3. Use of safer chemicals

4. Use of safer solvents and auxiliaries

5. Design for energy efficiency

6. Renewable feedstocks

7. Less hazardous chemical synthesis

8. Reduce derivatives

9. Catalysis

10. Atom economy

11. Real-time analysis

12. Accident prevention

what are ionic liquids and deep eutectic solvents? give advantages

Ionic liquids

1. Liquid salts

2. Low melting points
   

Deep eutectic solvents

1. Mixtures

2. Reduced melting points

Advantages

• Low volatility and can dissolve biomass or CO₂

describe two ways CO2 can be utilized and one limitation

Converted into fuels such as methanol or hydrocarbons or stored as carbonates

1. Methanol

   1. CO₂ + 3H₂ → CH₃OH + H₂O

2. Mineralization (Carbonate)

   1. CO₂ + Ca₂ + H₂O → CaCO₃ + 2H

CO2 is very stable and requires high energy for conversion

compare AEL, AEM, PEM, and high-temperature electrolysis

AEL

1. liquid alkaline

2. Cheap, old, and slow

3. OH^-

AEM

1. solid membrane

2. new, like AEL but compact

3. OH^-

PEM

1. solid membrane

2. Expensive catalysts and fast

3. H⁺

High-temperature electrolysis

1. Solid membrane (ceramic)

2. ~95% efficiency

3. Heat source required

4. O^2-

why is ammonia considered a hydrogen carrier? Include reaction.

Ammonia is easier to store and transport than hydrogen due to its higher volumetric density

Releases hydrogen via decomposition

1. 2NH₃ → 3H₂ + N₂

Explain why cellulose is difficult to process and how it’s modified.

1. Strong hydrogen bonding

2. Strong crystalline structure

Modified by derivatization into esters or ethers to improve solubility and functionality

What is MICP? (Microbial Induced Carbonate Precipitation) Include reactions.

Microorganisms or enzymes like urease are used

Increases pH and converts CO₂ into carbonate ions that react with Ca²⁺+ to form CaCO₃

1. CO₂ → CO₃ ^2-

2. Ca²⁺ + CO₃ ^2- → CaCO₃

Why is direct seawater electrolysis not suitable?

Causes scaling from Mg²⁺ and Ca²⁺

Corrosion of electrodes

Low efficiency due to low conductivity

List and shortly explain possible methods for generating hydrogen from fossil and renewable resources, including the main reaction equations involved.

1. Fossil-based

   1. Steam methane reforming (1), followed by water-gas shift reaction (2)

      1. CH₄ + H₂O → CO + 3H₂

      2. CO + H₂O → CO₂ + H₂

   2. Coal gasification

      1. C + H₂O → CO + H₂

2. Renewable-based

   1. Water electrolysis (produces hydrogen)

      1. 2H₂O → 2H₂ + O₂

   2. Biomass conversion (produces syngas—CO + H₂)

      1. Biomass → syngas

What is green chemistry, and what is its main idea?

Design of chemical products and processes that reduce or eliminate hazardous substances

Prevent pollution at the source rather than treating it afterwards

What is the E-factor and what does it tell you?

Measures the amount of waste generated per unit of product

Lower E-factor = more environmentally friendly and efficient process

Why is catalysis important in green chemistry?

Increases reaction efficiency

Reduces energy use

Minimizes waste

They’re not consumed and improve selectivity compared to stoichiometric reagents

Why are solvents a problem, and what are examples of greener alternatives?

They contribute to most of the waste and can be toxic to the environment

Green alternatives include water, ionic liquids, and deep eutectic solvents

What does design for degradation mean? Give one examples

Chemicals should break down into harmless products after use; be biodegradable

Example: PLA is a biodegradable polymer with an ester backbone

Why is real-time analysis important in green chemistry?

Monitors reactions continuously to prevent formation of hazardous by-products

Improves safety, efficiency, and pollution prevention

Compare atom economy and E-factor

Atom economy is how many atoms from reactants end up in the product, while E-factor measures the amount of waste produced

AE = theoretical

E-factor = process efficiency

Compare atom economy and percent yield

Atom economy is how many atoms from reactants end up in the percent yield measures how much product is obtained relative to the theoretical amount

Why is catalysis better than stoichiometric reagents?

They reduce waste, improve selectivity, lower energy use, cost-effective, environmentally friendly, and speed up reactions without being consumed (they regenerate)

Stoichiometric methods are consumed and converted into by-products, generating lots of waste

Give examples of green solvents

Water

Ionic liquids

Deep eutectic solvents

What is Life Cycle Assessment (LCA)

It’s a methodology that evaluates the environmental impact of a product from raw materials to production, use, and disposal over its entire lifespan— ‘cradle to grave’

What does ‘prevention of waste’ mean

Avoid the generation of waste instead of treating or cleaning it after it forms

What are renewable feedstocks

Raw materials from renewable sources such as biomass, CO₂, or waste instead of fossil fuels used in chemical processes

Why is designing safer chemicals important

Reduces toxicity while maintaining function, while improving safety for humans and the environment

Give one real-world example of green chemistry

Polylactic acid (PLA) is a biobased polymer made from renewable feedstocks and designed to degrade after use