Acid Base Salt -

📘 Study MCQs

Q1. The word ‘acid’ comes from the Latin word ‘acidus’. What is the meaning of ‘acidus’?

A. Sweet

B. Bitter

C. Sour

D. Salty

C. Sour

The Latin word “acidus” means sour, which reflects the characteristic sour taste of most acids, such as lemon juice or vinegar.

Q2. Which of the following is a natural acid found in curd?

A. Citric acid

B. Tartaric acid

C. Acetic acid

D. Lactic acid

Curd contains lactic acid, which is produced by the fermentation of milk by bacteria such as Lactobacillus, giving curd its characteristic sour taste.

Q3. Vinegar is a common substance in our kitchens. Which acid is present in it?

A. Citric acid

B. Tartaric acid

C. Acetic acid

D. Oxalic acid

C. Acetic acid

Vinegar contains acetic acid, which is produced by the fermentation of ethanol by acetic acid bacteria, giving vinegar its sour taste.

Q4. Lemons and oranges taste sour because they contain a specific acid. What is it?

A. Lactic acid

B. Citric acid

C. Tartaric acid

D. Ascorbic acid

B. Citric acid

Citrus fruits like lemons and oranges are rich in citric acid, a weak organic acid responsible for their sharp, sour flavor.

Q5. Tamarind is used as a souring agent in many Indian dishes. Which acid gives it this sour taste?

A. Citric acid

B. Lactic acid

C. Tartaric acid

D. Acetic acid

C. Tartaric acid

Tamarind contains tartaric acid, a naturally occurring organic acid that imparts a tangy, sour taste to foods.

Q6. What is the general name for acids that are obtained from natural sources like plants and animals?

A. Mineral acids

B. Strong acids

C. Organic acids

D. Weak acids

C. Organic acids

Organic acids are carbon-containing acids obtained from natural sources such as plants and animals, including citric acid, lactic acid, and acetic acid.

Q7. Acids that are prepared from minerals of the earth are called mineral acids. Which of these is a mineral acid?

A. Citric acid

B. Lactic acid

C. Acetic acid

D. Sulphuric acid

Mineral acids are inorganic acids derived from minerals; sulphuric acid (H₂SO₄) is a strong mineral acid widely used in industry.

Q8. Queen of Chemicals

A. King of Chemicals

Sulphuric acid is often called the “King of Chemicals” because of its extensive industrial use, including in fertilizers, batteries, and chemical manufacturing.

Q9. Nitric acid is another important mineral acid. In which of the following processes is it commonly used?

A. Making soaps

B. Manufacturing of fertilizers

C. Cooking food

D. Making window cleaners

B. Manufacturing of fertilizers

Nitric acid (HNO₃) is a key component in the production of nitrogen-based fertilizers such as ammonium nitrate.

Q10. Our stomach produces a mineral acid to help digest food. Which acid is this?

A. Sulphuric acid

B. Nitric acid

C. Phosphoric acid

D. Hydrochloric acid

Gastric glands in the stomach secrete hydrochloric acid (HCl), which creates an acidic environment for digestion and kills ingested bacteria.

Q11. Phosphoric acid is often used to add a tangy flavor to soft drinks. What is its chemical formula?

A. HCl

B. H₂SO₄

C. HNO₃

D. H₃PO₄

Phosphoric acid, with the chemical formula H₃PO₄, is a weak acid commonly added to carbonated beverages for tartness.

Q12. Which type of acids are the building blocks of fats and oils?

A. Amino acids

B. Nucleic acids

C. Fatty acids

D. Mineral acids

C. Fatty acids

Fatty acids are carboxylic acids that combine with glycerol to form fats and oils (triglycerides), serving as energy storage molecules.

Q13. Proteins are made up of smaller units. What are these units called?

A. Fatty acids

B. Amino acids

C. Sulphuric acid

D. Nucleic acids

B. Amino acids

Amino acids are organic compounds that serve as the monomers (building blocks) of proteins, linked together by peptide bonds.

Q14. The molecule that carries our genetic information is called DNA. What type of acid is DNA?

A. Fatty acid

B. Amino acid

C. Mineral acid

D. Nucleic acid

DNA (deoxyribonucleic acid) is a nucleic acid that stores and transmits genetic information in living organisms.

Q15. Soap is a common substance we use for bathing. What is the nature of a soap solution?

A. Acidic

B. Basic

C. Neutral

D. Slightly sour

B. Basic

Soap solutions are basic (alkaline) due to the presence of bases like sodium hydroxide or potassium hydroxide used in saponification.

Q16. Liquid soap often contains a base that is also found in window cleaners. Which base is this?

A. Sodium hydroxide

B. Calcium hydroxide

C. Magnesium hydroxide

D. Potassium hydroxide

Potassium hydroxide (KOH) is commonly used in liquid soaps and window cleaners due to its strong alkaline nature and solubility.

Q17. A white solid is used for whitewashing walls. When mixed with water, it forms limewater. What is this substance?

A. Sodium hydroxide

B. Calcium hydroxide

C. Magnesium hydroxide

D. Ammonium hydroxide

B. Calcium hydroxide

Calcium hydroxide (slaked lime) is used for whitewashing; its solution in water is called limewater.

Q18. Doctors prescribe ‘Milk of Magnesia’ to relieve acidity or indigestion. What is its chemical name?

A. Calcium hydroxide

B. Sodium hydroxide

C. Magnesium hydroxide

D. Ammonium hydroxide

C. Magnesium hydroxide

Milk of Magnesia is a suspension of magnesium hydroxide (Mg(OH)₂), an antacid that neutralizes excess stomach acid.

Q19. A base is used in the manufacturing of soaps and is a key ingredient in drain cleaners. Its chemical formula is NaOH. What is its common name?

A. Potassium hydroxide

B. Calcium hydroxide

C. Sodium hydroxide

D. Ammonium hydroxide

C. Sodium hydroxide

Sodium hydroxide (caustic soda) is a strong base used in soap making, paper production, and drain cleaners.

Q20. Many window cleaning solutions contain a base with the formula NH₄OH. What is its chemical name?

A. Sodium hydroxide

B. Calcium hydroxide

C. Magnesium hydroxide

D. Ammonium hydroxide

Ammonium hydroxide (NH₄OH) is a weak base commonly used in household cleaning products, including window cleaners.

Q21. What is the general name for a substance, like litmus or turmeric, that changes color to show whether a solution is acidic or basic?

A. Indicator

B. Catalyst

C. Reagent

D. Solvent

A. Indicator

Indicators are substances that change color in response to pH, allowing identification of acidic or basic solutions.

Q22. Litmus is a natural dye extracted from a plant. What is its original color?

A. Red

B. Blue

C. Purple

D. Green

C. Purple

Natural litmus is a purple dye extracted from lichens (primarily Roccella and Lecanora species).

Q23. A student adds a drop of a liquid to a red litmus paper. The paper turns blue. What is the nature of the liquid?

A. Acidic

B. Basic

C. Neutral

D. Sour

B. Basic

Bases turn red litmus paper blue, indicating an alkaline nature.

Q24. A student adds a drop of a liquid to a blue litmus paper. The paper turns red. What is the nature of the liquid?

A. Acidic

B. Basic

C. Neutral

D. Soapy

A. Acidic

Acids turn blue litmus paper red, indicating an acidic nature.

Q25. A solution is tested with both red and blue litmus papers, and neither paper changes color. What is the solution?

A. Acidic

B. Basic

C. Neutral

D. Can’t say

C. Neutral

Neutral solutions (like pure water) do not change the color of either red or blue litmus paper.

Q26. Soap solution turns the color of ______ litmus paper to blue.

A. Blue

B. Red

C. Green

D. Yellow

B. Red

Soap solution is basic, so it turns red litmus paper blue.

Q27. What effect does lemon juice, an acid, have on blue litmus paper?

A. Turns it blue

B. Turns it red

C. No change

D. Turns it green

B. Turns it red

Lemon juice contains citric acid, which turns blue litmus paper red.

Q28. Turmeric is a natural indicator used in Indian kitchens. Its paste is yellow. What color does it turn when a basic solution like soap is added to it?

A. Yellow

B. Green

C. Red

D. Blue

C. Red

Turmeric contains curcumin, which turns reddish-brown in basic solutions.

Q29. A woman’s white saree gets a yellow stain of turmeric during a festival. Later, while washing, her soapy hands accidentally rub the stain. What will happen to the stain?

A. It will become darker red

B. It will disappear completely

C. It will turn green

D. Nothing will happen

A. It will become darker red

Turmeric stain turns reddish-brown when it comes into contact with the soap solution (basic), making it appear darker.

Q30. China rose is an indicator. Its solution is generally ______ in color.

A. Red

B. Yellow

C. Green

D. Light pink or magenta

The petals of China rose (Hibiscus rosa-sinensis) yield a light pink or magenta colored solution when soaked in water.

Q31. When an acid is added to a China rose indicator, what color change is observed?

A. Green

B. Dark pink (Magenta)

C. Yellow

D. Blue

B. Dark pink (Magenta)

China rose indicator turns dark pink or magenta in acidic solutions.

Q32. When a base is added to a China rose indicator, what color change is observed?

A. Dark pink (Magenta)

B. Green

C. Red

D. No change

B. Green

China rose indicator turns green in basic solutions.

Q33. You have a China rose indicator (magenta color). You add it to a sample of tap water and the color changes to green. What does this tell you about the tap water?

A. It is acidic

B. It is basic

C. It is neutral

D. It is pure

B. It is basic

Green color indicates that the tap water is basic (alkaline), possibly due to dissolved minerals.

Q34. Which of the following is NOT a natural indicator?

A. Litmus

B. Turmeric

C. Phenolphthalein

D. China rose

C. Phenolphthalein

Phenolphthalein is a synthetic indicator, while litmus, turmeric, and China rose are obtained from natural sources.

Q35. A substance tastes sour and turns blue litmus red. It is likely to be ______.

A. Lemon juice

B. Soap

C. Baking soda

D. Water

A. Lemon juice

Sour taste and turning blue litmus red are characteristic properties of acids, such as the citric acid in lemon juice.

Q36. A substance feels soapy to touch and turns red litmus blue. It is likely to be ______.

A. Vinegar

B. Orange juice

C. Soap solution

D. Lemon juice

C. Soap solution

Soapy feel and turning red litmus blue are characteristic properties of bases.

Q37. What is the nature of a substance that does not change the color of either red or blue litmus paper?

A. Acidic

B. Basic

C. Neutral

D. Sour

C. Neutral

Neutral substances (like water, salt solution) do not affect the color of litmus paper.

Q38. Which of the following eatable substances contains oxalic acid?

A. Lemon

B. Vinegar

C. Tomato

D. Spinach

Spinach is rich in oxalic acid, a naturally occurring organic acid found in many leafy green vegetables.

Q39. What type of acid is ascorbic acid, which is commonly known as Vitamin C?

A. Mineral acid

B. Organic acid

C. Strong acid

D. Fatty acid

B. Organic acid

Ascorbic acid is an organic acid naturally found in citrus fruits and is essential for human health as Vitamin C.

Q40. The image shows a bottle of a soft drink. Which acid, besides carbonic acid, is commonly found in these drinks to give them a tangy flavor?

A. Lactic acid

B. Tartaric acid

C. Phosphoric acid

D. Acetic acid

C. Phosphoric acid

Many soft drinks contain phosphoric acid (H₃PO₄) to provide a tangy flavor and act as a preservative.

Q41. A gardener wants to reduce the acidity of his garden soil. Which substance should he add?

A. Vinegar

B. Lemon juice

C. Lime (Calcium hydroxide)

D. Water

C. Lime (Calcium hydroxide)

Lime (calcium hydroxide) is a base that neutralizes acidic soil, raising the pH to a level suitable for plant growth.

Q42. An ant sting injects methanoic acid into the skin. What natural remedy can be used to neutralize it?

A. Vinegar

B. Lemon juice

C. Rubbing with baking soda paste

D. Water

C. Rubbing with baking soda paste

Baking soda (sodium bicarbonate) is basic and helps neutralize the methanoic acid from ant stings, providing relief.

Q43. Why is it dangerous to mix acids with bases directly?

A. They produce a large amount of gas

B. They produce a large amount of heat (exothermic reaction)

C. They change color

D. They become neutral

B. They produce a large amount of heat (exothermic reaction)

Neutralization reactions between acids and bases are highly exothermic, releasing significant heat that can cause burns or violent splattering.

Q44. A beaker contains a colorless liquid. A drop of it on a turmeric paper turns it reddish-brown. What is the nature of the liquid?

A. Acidic

B. Basic

C. Neutral

D. Sour

B. Basic

Turmeric paper turns reddish-brown in basic solutions, indicating the liquid is basic.

Q45. Which base is commonly known as ‘caustic soda’ and has the chemical formula NaOH?

A. Potassium hydroxide

B. Calcium hydroxide

C. Magnesium hydroxide

D. Sodium hydroxide

Sodium hydroxide (NaOH) is commonly called caustic soda due to its corrosive nature and is widely used in soap making and cleaning agents.

Q46. Which acid is known as the ‘King of Chemicals’ and is used in car batteries?

A. Hydrochloric acid

B. Nitric acid

C. Sulphuric acid

D. Phosphoric acid

C. Sulphuric acid

Sulphuric acid (H₂SO₄) is called the “King of Chemicals” due to its extensive industrial applications, including use in lead-acid car batteries.

Q47. What is the chemical name and formula for the base found in ‘Milk of Magnesia’?

A. Sodium hydroxide, NaOH

B. Calcium hydroxide, Ca(OH)₂

C. Magnesium hydroxide, Mg(OH)₂

D. Ammonium hydroxide, NH₄OH

C. Magnesium hydroxide, Mg(OH)₂

Milk of Magnesia is a suspension of magnesium hydroxide used as an antacid.

Q48. Which base is used in the process of whitewashing walls and its solution is known as limewater?

A. Sodium hydroxide

B. Potassium hydroxide

C. Calcium hydroxide

D. Ammonium hydroxide

C. Calcium hydroxide

Calcium hydroxide (slaked lime) is used for whitewashing; its aqueous solution is called limewater.

Q49. Acids react with metals to produce a gas. Which gas is produced?

A. Oxygen

B. Nitrogen

C. Carbon dioxide

D. Hydrogen

Acids react with reactive metals to produce hydrogen gas (e.g., Zn + 2HCl → ZnCl₂ + H₂↑).

Q50. If a liquid has a pH of 7, what is its nature?

A. Strongly acidic

B. Strongly basic

C. Neutral

D. Weakly acidic

C. Neutral

A pH of 7 indicates a neutral solution, such as pure water, where the concentration of H⁺ and OH⁻ ions is equal.