Alcohol Archives

1. Which one of the following is known as Wood Spirit ?

Which one of the following is known as Wood Spirit ?

Methanol

Ethanol

Formaldehyde

Acetaldehyde

This question was previously asked in

UPSC CAPF – 2019

Download PDF Attempt Online

Methanol (CH3OH) is historically known as wood alcohol or wood spirit because it was traditionally produced by the destructive distillation of wood.

– Methanol is the simplest alcohol.
– It is a volatile, flammable, poisonous liquid.
– Its historical source gave it the common name “wood spirit”.

Ethanol (C2H5OH) is grain alcohol, commonly found in alcoholic beverages. Formaldehyde (HCHO) is an aldehyde used as a preservative and disinfectant. Acetaldehyde (CH3CHO) is another aldehyde, toxic and a metabolic product of ethanol breakdown.

2. Sometimes, the consumption of local made alcoholic beverages may cause

Sometimes, the consumption of local made alcoholic beverages may cause blindness or even death. This may be because of contamination of the beverages with :

Vinegar

Carbolic acid

Methyl alcohol

Formic acid

This question was previously asked in

UPSC CAPF – 2009

Download PDF Attempt Online

Blindness or death from consuming local made alcoholic beverages may be because of contamination with Methyl alcohol.

Ethanol (ethyl alcohol) is the alcohol intended for consumption in alcoholic beverages. Methanol (methyl alcohol) is a highly toxic substance that can be produced as a byproduct during improper fermentation or distillation, or sometimes illegally added to beverages. When ingested, methanol is metabolized by the body into formaldehyde and formic acid, which are potent toxins that damage the optic nerve (leading to blindness) and other organs, often resulting in death.

Vinegar is primarily acetic acid, which is relatively harmless in small quantities. Carbolic acid is phenol, a highly corrosive and toxic chemical. Formic acid is one of the toxic metabolites of methanol, but the primary contamination is usually with methanol itself.

3. What is the action of litmus on ethanol ?

What is the action of litmus on ethanol ?

Litmus is neutral towards ethanol

Ethanol turns blue litmus to red; confirming acidic nature of ethanol

Ethanol turns red litmus to blue; confirming basic nature of ethanol

Ethanol decolorizes litmus through bleaching action

This question was previously asked in

UPSC NDA-2 – 2023

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A) Litmus is neutral towards ethanol.

– Litmus is an acid-base indicator. It turns red in acidic solutions (pH < 7) and blue in basic solutions (pH > 7).
– Ethanol (C₂H₅OH) is an alcohol. The -OH group in alcohols is covalently bonded, unlike the ionic hydroxide in strong bases (e.g., NaOH).
– Alcohols are generally considered neutral compounds in aqueous solutions. While they can act as very weak acids (donating a proton from the -OH group, especially when reacting with strong bases like alkali metals) or very weak bases (accepting a proton from a strong acid at the oxygen atom), their acidity or basicity is negligible in the context of affecting litmus paper pH indicators.

– Ethanol does not dissociate significantly in water to produce H⁺ ions (acidic) or OH⁻ ions (basic).
– Therefore, when litmus paper is placed in ethanol or an aqueous solution of ethanol, its color remains unchanged (red litmus stays red, blue litmus stays blue), indicating a neutral pH.
– Ethanol does not possess bleaching properties like chlorine-based compounds.