Acids, Bases and Salts — Class 10 Science MCQ with Answers (2026-27)

Updated 23 August 2026 · checked against the CBSE 2026-27 syllabus

10 objective questions on Acids, Bases and Salts (Class 10 Science — Chemistry), every one checked against the CBSE 2026-27 syllabus. Pick an option and the correct answer is shown straight away, with your marks running at the top.

Acids, Bases and Salts MCQ questions with answers

1. Builders use plaster of Paris to make the surface layer of the inner walls of a building. Which property of plaster​ of Paris​ powder makes it a suitable building material?
   1. It is lightweight.
   2. It is white in colour.
   3. It is found readily in nature.
   4. It gets hard when mixed with water.

   Answer: d) It gets hard when mixed with water.

   Plaster of Paris sets into a hard solid when water is added because it changes to gypsum. That setting action is what makes it useful for surfacing walls.

2. Which statement about litmus‌ in‌ acids and bases is correct?
   1. Acids turn blue litmus red and bases turn red litmus blue
   2. Acids turn blue litmus red and bases turn blue litmus red
   3. Acids turn red litmus blue and bases turn red litmus blue
   4. Acids turn red litmus blue and bases turn blue litmus red

   Answer: a) Acids turn blue litmus red and bases turn red litmus blue

   The standard test: an acid turns blue litmus red, and a base turns red litmus blue. Each changes only the colour it can affect.

3. The acidic properties​​ of hydrochloric acid are due to the concentration of
   1. hydrogen ions
   2. chloride ions
   3. bromide ions
   4. nitrate ions

   Answer: a) hydrogen ions

   An acid is acidic because it releases H⁺ ions in water. The chloride ion plays no part in the acidic behaviour, which is why dry HCl gas is not acidic.

4. Rama gives Seeta two test tubes. One contains water and the other a dilute solution of sodium hydroxide.
   Which test should Seeta use to identify the sodium‌​ hydroxide solution?
   1. Blue litmus solution
   2. Baking soda solution
   3. Dilute soap solution
   4. Red litmus solution

   Answer: d) Red litmus solution

   Sodium hydroxide is a base, and a base turns red litmus blue. Blue litmus would show no change and so could not identify it.

5. Chlorine gas reacts with _______‌ to​ form bleaching powder.
   1. dry Ca(OH)₂
   2. dilute solution of Ca(OH)₂
   3. concentrated solution of Ca(OH)₂
   4. dry CaO

   Answer: a) dry Ca(OH)₂

   Bleaching powder is made by passing chlorine over dry slaked lime: Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O. Using a solution instead would not give the product.

6. What will happen​ if​ dry HCl gas is taken instead of an aqueous solution of HCl?
   1. The reaction will occur faster.
   2. The reaction will not occur.
   3. The reaction rate will be slow.
   4. The reaction rate will remain the same.

   Answer: b) The reaction will not occur.

   An acid only shows acidic behaviour when it releases H⁺ ions, which needs water. Dry HCl gas has no free H⁺ ions, so no reaction takes place.

7. Toxic foam forms on the Yamuna because of the high phosphate content of wastewater from detergents used by dyeing industries, dhobi ghats and households.
   Predict the pH value​‌ of the water of the river Yamuna if the froth is caused by a high content of dissolved detergents.
   1. 10–11
   2. 5–7
   3. 2–5
   4. 7

   Answer: a) 10–11

   Detergents are basic, so dissolving a lot of them pushes the pH above 7. A value of 10-11 is in the basic range; anything below 7 would be acidic.

8. Which statement is correct for water with‌‌ detergents dissolved in it?
   1. Low concentration of OH⁻ and high concentration of H₃O⁺
   2. High concentration of OH⁻ and low concentration of H₃O⁺
   3. High concentration of both OH⁻ and H₃O⁺
   4. Equal concentration of OH⁻ and H₃O⁺

   Answer: b) High concentration of OH⁻ and low concentration of H₃O⁺

   A basic solution has more OH⁻ than H₃O⁺ ions. Since detergents make the water basic, OH⁻ is high and H₃O⁺ is correspondingly low.

9. Four solutions have these pH values — P: 2, Q: 9, R: 5, S: 11.
   Which option correctly represents the solutions in increasing order​​ of hydronium ion concentration?
   1. P > Q > R > S
   2. P > S > Q > R
   3. S < Q < R < P
   4. S < P < Q < R

   Answer: c) S < Q < R < P

   The lower the pH, the higher the hydronium concentration. With P = 2, R = 5, Q = 9 and S = 11, increasing H₃O⁺ runs from the highest pH to the lowest: S < Q < R < P.

10. If a sample of water​‌ containing detergents is provided to you, which method will you adopt to neutralise it?
    1. Treating the water with baking soda
    2. Treating the water with vinegar
    3. Treating the water with caustic soda
    4. Treating the water with washing soda

    Answer: b) Treating the water with vinegar

    Neutralising a base needs an acid. Vinegar contains acetic acid, whereas baking soda, caustic soda and washing soda are all basic and would make it worse.