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Acids, Bases & Salts — Homi Bhabha Class 9 Chemistry MCQs with Solutions
Free Homi Bhabha Class 9 Chemistry Acids, Bases & Salts MCQs with step-by-step solutions covering Indicators, pH Scale, Chemical Properties, Neutralization, Everyday Salts. Practise online on Prepizo — no login needed.
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Sample questions with solutions
Q1 — Indicators · easy · theory
A student dips a strip of blue litmus paper into an unknown solution and it turns red. The solution must be:
A. Acidic ✓ Correct
B. Neutral
C. A concentrated salt solution
D. Basic
Solution: Blue litmus turns red only in acidic solutions; bases keep it blue and neutral solutions cause no change.
Q2 — Indicators · easy · theory
A few drops of phenolphthalein are added to a colourless solution and it immediately turns pink. The solution is most likely:
A. Pure water
B. Sodium hydroxide solution ✓ Correct
C. Lemon juice
D. Dilute hydrochloric acid
Solution: Phenolphthalein stays colourless in acidic and neutral solutions and turns pink only in basic solutions such as sodium hydroxide.
Q3 — pH Scale · easy · theory
On the pH scale, the pH of a neutral solution such as pure water at 25°C is:
A. 0
B. 1
C. 7 ✓ Correct
D. 14
Solution: A neutral solution has equal H+ and OH- ions and a pH of 7 at 25°C; below 7 is acidic and above 7 is basic.
Q4 — Chemical Properties · easy · theory
When a dilute acid reacts with an active metal such as zinc, a gas is released that burns with a pop sound. This gas is:
A. Carbon dioxide
B. Oxygen
C. Chlorine
D. Hydrogen ✓ Correct
Solution: Metals react with dilute acids to form a salt and hydrogen gas; hydrogen is the gas that burns with a characteristic pop sound.
Q5 — Neutralization · easy · theory
The reaction in which an acid and a base react together to produce a salt and water is called:
A. Corrosion
B. Oxidation
C. Neutralization ✓ Correct
D. Displacement
Solution: An acid plus a base gives a salt and water; this type of reaction is known as neutralization.
Q6 — Everyday Salts · easy · theory
The common salt sprinkled on food for taste is chemically known as:
A. Sodium chloride ✓ Correct
B. Calcium carbonate
C. Sodium bicarbonate
D. Sodium hydroxide
Solution: Common table salt is sodium chloride (NaCl), formed from hydrochloric acid and sodium hydroxide.
Q7 — Everyday Salts · easy · theory
Baking soda, which is used in cooking and also as a mild antacid, is chemically:
A. Calcium sulphate
B. Sodium hydrogen carbonate ✓ Correct
C. Sodium carbonate
D. Sodium chloride
Solution: Baking soda is sodium hydrogen carbonate (sodium bicarbonate, NaHCO3), a mild base used in cooking and to relieve acidity.
Q8 — Indicators · hard · theory
Phenolphthalein remains colourless in acidic solution but turns ______ in a basic solution:
A. red
B. pink ✓ Correct
C. yellow
D. blue
Solution: Phenolphthalein is colourless in acid and pink in base.
Q9 — Indicators · hard · theory
Methyl orange gives a ______ colour in an acidic solution:
A. yellow
B. green
C. red ✓ Correct
D. blue
Solution: Methyl orange is red in acid and yellow in base.
Q10 — Indicators · hard · theory
Substances like onion and vanilla, whose smell changes in acidic or basic media, are called:
A. olfactory indicators ✓ Correct
B. litmus
C. salts
D. universal indicators
Solution: Olfactory indicators show a change in odour to detect acids and bases.
Q11 — pH Scale · hard · theory
Of two solutions, one has pH 2 and the other pH 5. The more acidic solution is the one with pH:
A. 5
B. neither is acidic
C. both are equal
D. 2 ✓ Correct
Solution: Lower pH means greater acidity, so pH 2 is more acidic than pH 5.
Q12 — pH Scale · hard · theory
A solution turns red litmus blue. Its pH is most likely:
A. exactly 0
B. greater than 7 ✓ Correct
C. less than 7
D. exactly 7
Solution: Turning red litmus blue indicates a base, which has pH greater than 7.
Q13 — Chemical Properties · hard · theory
The gas evolved when an acid reacts with a metal carbonate (e.g. limestone) is:
A. carbon dioxide ✓ Correct
B. oxygen
C. chlorine
D. hydrogen
Solution: Acid + carbonate → salt + water + carbon dioxide, which turns lime water milky.
Q14 — Chemical Properties · hard · theory
The gas produced when a metal reacts with an acid is tested by bringing a burning splint near it; a positive test gives:
A. a milky colour
B. a "pop" sound ✓ Correct
C. a red colour
D. a green flame
Solution: Hydrogen gas burns with a characteristic "pop" sound.
Q15 — Chemical Properties · hard · theory
Acids conduct electricity in aqueous solution because they:
A. are metals
B. produce no ions
C. produce ions (H⁺) in water ✓ Correct
D. contain oxygen only
Solution: Acids ionise in water to give mobile ions (including H⁺), which carry the current.
Q16 — Neutralization · hard · theory
Hydrochloric acid reacts with sodium hydroxide to give:
A. sodium and chlorine
B. sodium chloride and water ✓ Correct
C. sodium carbonate
D. hydrogen and oxygen
Solution: HCl + NaOH → NaCl + H₂O (a neutralisation).
Q17 — Neutralization · hard · theory
A bee sting, which is acidic, can be soothed by applying:
A. baking soda (a mild base) ✓ Correct
B. common salt
C. vinegar (an acid)
D. lemon juice (an acid)
Solution: A mild base like baking soda neutralises the acidic sting.
Q18 — Neutralization · hard · theory
Toothpastes are usually basic in nature so that they can:
A. dissolve the teeth
B. produce hydrogen gas
C. neutralise the acids formed by bacteria in the mouth ✓ Correct
D. increase mouth acidity
Solution: Basic toothpaste neutralises acids that would otherwise attack tooth enamel.
Q19 — Everyday Salts · hard · theory
Washing soda, used for cleaning, is chemically:
A. sodium carbonate (Na₂CO₃·10H₂O) ✓ Correct
B. sodium chloride
C. calcium hydroxide
D. sodium hydrogen carbonate
Solution: Washing soda is hydrated sodium carbonate, Na₂CO₃·10H₂O.
Q20 — Everyday Salts · hard · theory
Bleaching powder, used to disinfect water, is chemically:
A. sodium carbonate
B. sodium chloride
C. calcium oxychloride (CaOCl₂) ✓ Correct
D. calcium carbonate
Solution: Bleaching powder is calcium oxychloride, CaOCl₂.
Q21 — Indicators · hard · theory
Three solutions P, Q and R are tested with litmus. Red litmus turns blue only in P, blue litmus turns red only in Q, and neither litmus changes colour in R. The correct identification of P, Q and R is:
A. P acidic, Q basic, R neutral
B. P basic, Q acidic, R neutral ✓ Correct
C. P neutral, Q acidic, R basic
D. P basic, Q neutral, R acidic
Solution: Red litmus turning blue means P is basic; blue litmus turning red means Q is acidic; no change in either litmus means R is neutral.
Q22 — pH Scale · hard · numerical
Solution A has a pH of 3 and solution B has a pH of 6. The hydrogen ion concentration of solution A is how many times that of solution B?
A. 3 times
B. 30 times
C. 300 times
D. 1000 times ✓ Correct
Solution: Each unit drop in pH multiplies the H+ concentration by 10. A difference of 3 pH units means 10³ = 1000 times greater H+ concentration in A.
Q23 — Chemical Properties · hard · theory
Assertion: Dry hydrogen chloride gas does not turn dry blue litmus paper red, but its water solution does. Reason: An acid shows acidic behaviour only when it is dissolved in water, where it can produce hydrogen (H+) ions. Which is correct?
A. Both are true, but the reason does not explain the assertion
B. The assertion is false but the reason is true
C. The assertion is true but the reason is false
D. Both assertion and reason are true, and the reason correctly explains the assertion ✓ Correct
Solution: Acids need water to release H+ ions, which are responsible for acidic behaviour. Dry HCl gas has no free H+ ions, so it cannot change dry litmus; the reason correctly explains the assertion.
Q24 — Chemical Properties · hard · theory
A certain element M reacts with dilute hydrochloric acid to release hydrogen gas, and the oxide of M reacts with the same acid to give only a salt and water. From this information, the correct conclusion is that M is:
A. A non-metal whose oxide is acidic
B. A non-metal whose oxide is neutral
C. A metal whose oxide is acidic
D. A metal whose oxide is basic ✓ Correct
Solution: Only metals displace hydrogen from acids, and a basic (metal) oxide reacts with acid to give just salt and water. Both clues show M is a metal with a basic oxide.
Q25 — Neutralization · hard · theory
When a strong acid is exactly neutralized by a strong base, the pH of the final solution and the temperature change observed are:
A. pH equal to 7, and the temperature rises ✓ Correct
B. pH less than 7, and the temperature rises
C. pH more than 7, and no change in temperature
D. pH equal to 7, and the temperature falls
Solution: Exact neutralization of a strong acid and strong base gives a neutral solution of pH 7, and because neutralization is exothermic, heat is released and the temperature rises.
Q26 — Everyday Salts · hard · theory
Washing soda (sodium carbonate) dissolves in water to give a solution that turns red litmus blue. This tells us that the salt is:
A. Neutral, formed from a weak acid and a weak base
B. Basic, formed from a strong base and a weak acid ✓ Correct
C. Neutral, formed from a strong acid and a strong base
D. Acidic, formed from a strong acid and a weak base
Solution: Turning red litmus blue shows the solution is basic. Sodium carbonate is the salt of a strong base (sodium hydroxide) and a weak acid (carbonic acid), so its solution is basic.
Q27 — Indicators · medium · theory
An acid turns blue litmus paper:
A. green
B. blue
C. red ✓ Correct
D. colourless
Solution: Acids turn blue litmus red; bases turn red litmus blue.
Q28 — Indicators · medium · theory
A base turns red litmus paper:
A. yellow
B. blue ✓ Correct
C. red
D. colourless
Solution: Bases turn red litmus blue.
Q29 — Indicators · medium · theory
Which of the following is a natural indicator?
A. Turmeric ✓ Correct
B. Methyl orange
C. Universal indicator
D. Phenolphthalein
Solution: Turmeric (like red cabbage and china rose) is a natural indicator; the others are synthetic.
Q30 — pH Scale · medium · theory
The pH scale is used to measure the ______ of a solution and ranges from:
A. temperature; 0 to 100
B. acidity or basicity; 0 to 14 ✓ Correct
C. mass; 0 to 7
D. density; 1 to 10
Solution: The pH scale (0–14) indicates how acidic or basic a solution is.