Detergents

PYQ-Based MCQs (Q1–10)

Detergents are:
a) Natural cleaning agents
b) Synthetic cleaning agents
c) Minerals
d) Organic acids
✅ b) Synthetic cleaning agents
Explanation: Detergents are man-made cleansing agents commonly used in households.
(BPSC 2020)
Which of the following is more effective in hard water?
a) Soap
b) Detergent
c) Shampoo
d) Vinegar
✅ b) Detergent
Explanation: Detergents do not form scum with calcium and magnesium ions in hard water.
(BPSC Teacher 2023)
Detergents are salts of:
a) Carboxylic acids
b) Sulfonic acids
c) Hydrochloric acid
d) Nitric acid
✅ b) Sulfonic acids
Explanation: Most synthetic detergents are alkyl benzene sulfonates.
(BPSC 66th Prelims)
Detergents are preferred over soaps because:
a) They smell better
b) They are cheaper
c) They work in hard water
d) They lather more
✅ c) They work in hard water
Explanation: Detergents remain effective in both soft and hard water.
(CDPO 2018)
Which of these is a cationic detergent?
a) Sodium lauryl sulfate
b) Cetyl trimethyl ammonium bromide
c) Sodium stearate
d) Potassium oleate
✅ b) Cetyl trimethyl ammonium bromide
Explanation: It contains a positively charged quaternary ammonium group.
(BPSC Assistant 2019)
A detergent molecule has:
a) Only hydrophilic part
b) Only hydrophobic part
c) Both hydrophilic and hydrophobic parts
d) Neither
✅ c) Both hydrophilic and hydrophobic parts
Explanation: The dual nature allows it to remove oily stains.
(BPSC 65th)
Anionic detergents are made from:
a) Fats
b) Hydrocarbons
c) Sulfonic acids
d) Ammonia
✅ c) Sulfonic acids
Explanation: They contain sulfonate groups that ionize in water.
(CDPO 2017)
Detergents act as:
a) Oxidizers
b) Disinfectants
c) Emulsifiers
d) Catalysts
✅ c) Emulsifiers
Explanation: They allow oil and water to mix by reducing surface tension.
(BPSC Teacher 2022)
Excessive use of detergents leads to:
a) Eutrophication
b) Radioactivity
c) Global warming
d) Ozone depletion
✅ a) Eutrophication
Explanation: Phosphates in detergents promote algal blooms in water bodies.
(BPSC 67th)
Which of the following is biodegradable?
a) Linear alkyl benzene detergent
b) Branched alkyl detergent
c) Synthetic plastic
d) PVC
✅ a) Linear alkyl benzene detergent
Explanation: Linear chains are more easily decomposed by microbes.

NCERT-Based MCQs (Q11–30)

Detergents are better than soaps because they:
a) Are made from animal fat
b) Can be used in acidic water
c) Are biodegradable
d) Have a lower pH
✅ b) Can be used in acidic water
Explanation: Unlike soap, detergent doesn't lose efficiency in acidic conditions.
Soap is prepared from:
a) Sulfuric acid and alcohol
b) Fats and alkali
c) Alcohol and acid
d) Glycerol
✅ b) Fats and alkali
Explanation: Saponification of fats with alkali produces soap.
Synthetic detergents are classified into how many categories?
a) 2
b) 3
c) 4
d) 5
✅ b) 3
Explanation: Anionic, cationic, and non-ionic are the main classes.
Which is a major disadvantage of detergents?
a) Low cost
b) Effective in hard water
c) Non-biodegradability
d) High lather
✅ c) Non-biodegradability
Explanation: Some detergents are harmful as they persist in the environment.
Which part of detergent dissolves grease?
a) Polar head
b) Hydrophilic tail
c) Non-polar tail
d) Ionic head
✅ c) Non-polar tail
Explanation: The non-polar tail binds with grease and oil molecules.
Which part of detergent dissolves in water?
a) Hydrocarbon tail
b) Non-polar end
c) Ionic (polar) head
d) Neutral group
✅ c) Ionic (polar) head
Explanation: The ionic head is attracted to water molecules.
Non-ionic detergents are used in:
a) Acidic soils
b) High-temperature cleaning
c) Food industries
d) Nuclear plants
✅ c) Food industries
Explanation: They are non-reactive and safe for food contact.
Which of the following causes foaming in rivers?
a) Soap
b) Plastic
c) Detergents
d) Oils
✅ c) Detergents
Explanation: Surfactants reduce surface tension, forming stable foam.
Surfactant molecules are:
a) Completely polar
b) Completely non-polar
c) Amphiphilic
d) Basic
✅ c) Amphiphilic
Explanation: They have both hydrophilic and hydrophobic parts.
Sodium lauryl sulfate is:
a) A soap
b) A detergent
c) A disinfectant
d) A salt
✅ b) A detergent
Explanation: It is a common anionic detergent used in shampoos and cleaners.
Which compound is the main surfactant in many household detergents?
a) Sodium stearate
b) Sodium lauryl sulfate
c) Sodium chloride
d) Glycerol
✅ b) Sodium lauryl sulfate
Explanation: It is an anionic surfactant widely used in detergents and toothpaste.
What allows detergents to break surface tension of water?
a) High pH
b) Emulsifying property
c) Hydrophobic tails
d) Surface-active agents
✅ d) Surface-active agents
Explanation: Surfactants in detergents reduce surface tension and allow better cleaning.
A detergent with linear chain alkyl group is:
a) More toxic
b) More stable
c) Non-biodegradable
d) Biodegradable
✅ d) Biodegradable
Explanation: Linear chain structures are easily broken down by microbes.
Which component of detergent causes pollution?
a) Water
b) Phosphate
c) Salt
d) Glycerine
✅ b) Phosphate
Explanation: Phosphates cause eutrophication in water bodies by feeding algae.
Detergents produce foam in:
a) Only soft water
b) Only distilled water
c) Hard and soft water
d) Only in hot water
✅ c) Hard and soft water
Explanation: They do not form scum and can lather well in all water types.
Excessive detergent in water bodies causes:
a) Global warming
b) Eutrophication
c) Acidity
d) Water hardness
✅ b) Eutrophication
Explanation: It encourages algal bloom, decreasing oxygen for aquatic life.
Which of the following is a major advantage of synthetic detergents?
a) High cost
b) Ineffective in hard water
c) No reaction with metal ions
d) Decomposes slowly
✅ c) No reaction with metal ions
Explanation: They don’t form precipitates with Ca²⁺ and Mg²⁺, unlike soaps.
What is added to detergents to improve cleansing in hard water?
a) Sodium chloride
b) Zeolites
c) Glycerine
d) Ammonia
✅ b) Zeolites
Explanation: Zeolites soften water by exchanging calcium/magnesium ions.
Which type of detergent is used in mouthwashes and disinfectants?
a) Anionic
b) Cationic
c) Non-ionic
d) Neutral
✅ b) Cationic
Explanation: Cationic detergents like cetyl trimethyl ammonium bromide act as antiseptics.
The cleaning action of detergent is due to:
a) Lowering boiling point
b) Reducing density
c) Breaking grease into small globules
d) Oxidizing fat
✅ c) Breaking grease into small globules
Explanation: It emulsifies oil, allowing it to be washed away with water.
Which detergent is safe for washing fruits?
a) Anionic detergent
b) Industrial detergent
c) Plant-based surfactant
d) Cationic detergent
✅ c) Plant-based surfactant
Explanation: These are non-toxic, biodegradable, and safe for cleaning edibles.
Non-biodegradable detergents are mostly:
a) Linear alkyl chains
b) Branched alkyl chains
c) Sulfonated long chains
d) Cationic types
✅ b) Branched alkyl chains
Explanation: Branching prevents microbial degradation, leading to persistence in the environment.
A detergent works better than soap in cold water because:
a) It dissolves easily
b) It forms scum
c) It is heavier
d) It has higher melting point
✅ a) It dissolves easily
Explanation: Detergents remain soluble and effective in cold or hard water.
Which of the following is a neutral detergent?
a) Anionic
b) Non-ionic
c) Cationic
d) Amphoteric
✅ b) Non-ionic
Explanation: These are electrically neutral and do not ionize in water.
Which part of detergent attacks oil/grease?
a) Ionic end
b) Carbon ring
c) Hydrocarbon tail
d) Alcoholic group
✅ c) Hydrocarbon tail
Explanation: The hydrophobic tail dissolves grease/oil, while the head binds with water.
Which detergent is best suited for delicate fabrics?
a) Non-ionic
b) Anionic
c) Cationic
d) Acidic
✅ a) Non-ionic
Explanation: These are milder and safer for delicate clothes and skin.
Role of builder in detergent:
a) Increase acidity
b) Soften hard water
c) Make it fragrant
d) Color the water
✅ b) Soften hard water
Explanation: Builders like phosphates bind metal ions and enhance detergent action.
Which detergent type is used in shampoos?
a) Anionic
b) Cationic
c) Non-ionic
d) Amphoteric
✅ a) Anionic
Explanation: They provide foaming and cleaning in personal care products.
Why are phosphates in detergents being banned?
a) They're expensive
b) Cause cancer
c) Cause water pollution
d) Reduce foam
✅ c) Cause water pollution
Explanation: Phosphates lead to eutrophication and fish death in rivers/lakes.
Eco-friendly detergent should be:
a) Chemically inert
b) Made from plastic
c) Biodegradable and phosphate-free
d) Colorless and odourless
✅ c) Biodegradable and phosphate-free
Explanation: Green detergents reduce harm to environment and aquatic life.