Chemistry Notes – Grade 10
National Curriculum Pakistan - NCP
Chapter 10: Hydroxy Compounds
Aligned with National Curriculum Pakistan (Federal Board, NBF, PTB)
Hydroxy Compounds Questions and Answers
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What is fermentation?
Fermentation is a process where yeast converts glucose into ethanol and carbon dioxide in the absence of oxygen. -
Write the equation for fermentation of glucose.
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ -
How is absolute ethanol obtained?
By using a dehydrating agent like concentrated H₂SO₄ to remove water from rectified spirit. -
Why is fermentation considered an environmentally friendly method for ethanol production?
It uses renewable plant materials, low energy, and emits fewer greenhouse gases, making it sustainable and eco-friendly. -
What are the drawbacks of using hydration of ethene for ethanol production?
It depends on crude oil, uses high energy, and has low ethene conversion efficiency (only about 4% per pass). -
Why does ethanol need to be purified after fermentation?
Because fermentation produces only 10–15% ethanol mixed with water and impurities, needing distillation and dehydration for purification. -
How does the structure of alcohols make them suitable as fuels?
Their hydrocarbon chains enable easy combustion, releasing energy, CO₂, and water—similar to fossil fuels. -
How does ethanol help reduce air pollution when used as a fuel?
It burns cleaner than petrol, producing less carbon monoxide and fewer pollutants, improving air quality. -
What makes alcohols suitable for pharmaceutical applications?
They dissolve both water-soluble and fat-soluble substances and act as disinfectants, making them ideal for use in medicines and sterilization. -
Why is methanol less suitable for direct use in engines than ethanol?
Methanol is more toxic, has lower energy output, and is corrosive to engines, requiring careful handling. -
How do alcohols act as antiseptics and disinfectants?
They denature microbial proteins and disrupt cell walls, killing bacteria, viruses, and fungi effectively. -
What are the environmental concerns with using fossil fuels instead of alcohols?
Fossil fuels are non-renewable and release large amounts of CO₂, causing global warming. Alcohols are renewable and burn cleaner. -
Why is ethanol used in the cosmetic industry?
Because of its antibacterial, antiviral, antimicrobial, and antifungal properties. -
Name any three cosmetic products that contain alcohol.
Deodorants, perfumes, and skin lotions. -
How do alcohols help cosmetic products?
They prevent ingredient separation and improve the product’s ability to adhere to the skin. -
How do alcohols contribute to hygiene?
They kill germs and are widely used in disinfectants and cleaning agents. -
Name one situation where alcohol-based disinfectants are very important.
During pandemics like COVID-19. -
Why are alcohol-based disinfectants easy to use?
They dry quickly and can be applied to many surfaces. -
What enzymes do in fermentation?
They convert glucose into ethanol and carbon dioxide. -
What is the ethanol concentration after fermentation?
10–15%. -
At what conditions is ethanol produced from ethene?
At 300°C and 6000 kPa using phosphoric acid as a catalyst. -
What is rectified spirit?
Ethanol that is 96% pure, separated by distillation. -
What is gasohol?
A fuel made by blending 10–20% ethanol with petrol. -
Why is ethanol better than gasoline in some ways?
It has a higher octane number and emits fewer harmful gases. -
What is the source of glucose used in fermentation?
Plants such as sugar cane (a renewable source). -
How is ethanol made from ethene?
By adding steam to ethene at 300°C and 6000 kPa using phosphoric acid as a catalyst. -
Write the equation for the hydration of ethene.
C₂H₄ + H₂O → C₂H₅OH -
What percentage of ethene is converted into ethanol in hydration?
Only 4%. -
Which method uses renewable resources—fermentation or hydration?
Fermentation. -
What is the raw material in the hydration of ethene?
Ethene from crude oil (non-renewable source). -
What is the raw material in the fermentation of glucose?
Glucose from plants like sugar cane (a renewable source). -
Which process is faster—hydration or fermentation?
Hydration. -
Which process produces pure ethanol?
Hydration of ethene. -
Which method requires more energy?
Hydration of ethene due to high temperature and pressure. -
Why do alcohols burn in air?
Due to the presence of a hydrocarbon chain. -
Write the combustion reaction of ethanol.
C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O + heat -
Which alcohol is used as an alternative fuel for cars?
Methanol. -
What is gasohol?
A fuel mixture of ethanol and gasoline. -
What is one advantage of ethanol fuel?
It reduces emissions of carbon monoxide and other pollutants. -
How much can corn-based ethanol reduce greenhouse gas emissions?
By roughly 40–50%. -
What is the disadvantage of using alcohol as fuel?
They can corrode engine materials due to being highly hygroscopic. -
Name two alcohols used as solvents in pharmacy.
Ethanol and isopropanol. -
What is isopropyl alcohol used for?
Disinfecting and sterilizing surfaces and equipment. -
What property makes alcohols useful against microbes?
They have antibacterial and antifungal properties. -
How do alcohols help in making medicines?
They dissolve active ingredients, making them easier to use. -
What are alcohol swabs used for?
To disinfect skin before injections or surgery.