According to the Arrhenius theory, an acid is a substance that

Produces H+ ions in aqueous solution

Acids, Bases and Salts MCQs 2026

52 questions with detailed answers · 19 from past papers · 6 quiz batches available

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Page 1 of 1Questions 1–10 of 52

Q1medium
Litmus paper turns ___ in basic solutions
1. ARed
2. BColorless
3. CYellow
4. DBlue
💡 Explanation:
Bases turn red litmus paper blue, a classic acid-base indicator test.
Q2medium
The conjugate base of an acid is formed when the acid
1. AGains a proton
2. BLoses a proton
3. CGains an electron pair
4. DLoses an electron pair
💡 Explanation:
After donating a proton, the remaining species is the conjugate base of the acid.
Q3Past Paper · PPSC/FPSC/NTSmedium
The conjugate acid of a base is formed when the base
1. ALoses a proton
2. BLoses an electron pair
3. CGains a proton
4. DGains hydroxide ions
💡 Explanation:
After accepting a proton, the base becomes its conjugate acid.
Q4Past Paper · PPSC/FPSC/NTSmedium
The conjugate acid of a base is formed when the base
1. ALoses a proton
2. BLoses an electron pair
3. CGains a proton
4. DGains hydroxide ions
💡 Explanation:
After accepting a proton, the base becomes its conjugate acid.
Q5easy
According to the Arrhenius theory, an acid is a substance that
1. AAccepts protons in solution
2. BProduces H+ ions in aqueous solution
3. CProduces OH- ions in aqueous solution
4. DAccepts electron pairs
💡 Explanation:
Arrhenius defined acids as substances that release H+ ions when dissolved in water.
Q6Past Paper · PPSC/FPSC/NTSeasy
According to the Arrhenius theory, a base is a substance that
1. AProduces OH- ions in aqueous solution
2. BProduces H+ ions in aqueous solution
3. CAccepts protons only in non-aqueous solvents
4. DDonates electron pairs only
💡 Explanation:
Arrhenius defined bases as substances that release OH- ions when dissolved in water.
Q7Past Paper · PPSC/FPSC/NTSeasy
According to the Bronsted-Lowry theory, an acid is defined as a
1. AProton acceptor
2. BElectron pair donor
3. CProton donor
4. DElectron pair acceptor
💡 Explanation:
Bronsted-Lowry theory broadens acids to any species that donates a proton.
Q8easy
According to the Bronsted-Lowry theory, a base is defined as a
1. AProton donor
2. BProton acceptor
3. CElectron pair acceptor
4. DSubstance producing OH- only
💡 Explanation:
Bronsted-Lowry theory defines a base as any species capable of accepting a proton.
Q9Past Paper · PPSC/FPSC/NTSeasy
According to the Lewis theory, a base is defined as a substance that
1. ADonates a proton
2. BDonates an electron pair
3. CAccepts a proton
4. DProduces H+ ions
💡 Explanation:
Lewis theory is the broadest definition, describing a base as an electron pair donor.
Q10easy
According to the Lewis theory, an acid is defined as a substance that
1. ADonates an electron pair
2. BProduces OH- ions
3. CDonates a proton only
4. DAccepts an electron pair
💡 Explanation:
Lewis acids are defined as electron pair acceptors, extending beyond proton-based definitions.
Q11Past Paper · PPSC/FPSC/NTSeasy
The pH scale ranges from
1. A1 to 10
2. B0 to 14
3. C0 to 7
4. D7 to 14
💡 Explanation:
The conventional pH scale spans from 0 (most acidic) to 14 (most basic).
Q12easy
A solution with pH less than 7 is
1. AAcidic
2. BBasic
3. CNeutral
4. DAmphoteric
💡 Explanation:
A pH value below 7 indicates an acidic solution.
Q13Past Paper · PPSC/FPSC/NTSeasy
A solution with pH greater than 7 is
1. AAcidic
2. BBasic
3. CNeutral
4. DUndefined
💡 Explanation:
A pH value above 7 indicates a basic (alkaline) solution.
Q14easy
Pure water at 25°C has a pH of
1. A0
2. B7
3. C14
4. D1
💡 Explanation:
Pure water is neutral, with equal H+ and OH- concentrations, giving a pH of 7 at 25°C.
Q15medium
pH is mathematically defined as
1. A[H+] × 10
2. Blog[H+]
3. C-log[H+]
4. D1/[H+]
💡 Explanation:
pH is defined as the negative base-10 logarithm of the hydrogen ion concentration.
Q16Past Paper · PPSC/FPSC/NTSmedium
The ionic product of water, Kw, at 25°C is
1. A1×10^-7
2. B1×10^0
3. C1×10^-14
4. D7×10^-14
💡 Explanation:
At 25°C, the ionic product of water Kw equals 1×10^-14.
Q17medium
A strong acid is one that
1. AHas a weak smell
2. BReacts slowly
3. CIs always concentrated
4. DIonizes completely in aqueous solution
💡 Explanation:
Strong acids fully dissociate into ions when dissolved in water.
Q18Past Paper · PPSC/FPSC/NTSmedium
A weak acid is one that
1. AIonizes completely
2. BHas no H+ ions
3. CIonizes only partially in aqueous solution
4. DIs always dilute
💡 Explanation:
Weak acids only partially dissociate, establishing an equilibrium in solution.
Q19medium
Which of the following is a strong acid
1. AHydrochloric acid (HCl)
2. BAcetic acid (CH3COOH)
3. CCarbonic acid (H2CO3)
4. DCitric acid
💡 Explanation:
Hydrochloric acid fully ionizes in water, making it a strong acid.
Q20medium
Which of the following is a weak acid
1. AAcetic acid
2. BSulfuric acid
3. CNitric acid
4. DHydrochloric acid
💡 Explanation:
Acetic acid only partially dissociates in water, classifying it as a weak acid.
Q21Past Paper · PPSC/FPSC/NTSmedium
Which of the following is a strong base
1. AAmmonium hydroxide
2. BSodium hydroxide (NaOH)
3. CAluminum hydroxide
4. DFerric hydroxide
💡 Explanation:
Sodium hydroxide fully dissociates in water, making it a strong base.
Q22medium
Which of the following is a weak base
1. ASodium hydroxide
2. BPotassium hydroxide
3. CCalcium hydroxide
4. DAmmonium hydroxide (NH4OH)
💡 Explanation:
Ammonium hydroxide only partially ionizes in water, classifying it as a weak base.
Q23medium
A salt is formed by the reaction between
1. AAn acid and a base
2. BTwo acids
3. CTwo bases
4. DWater and a metal only
💡 Explanation:
Neutralization of an acid with a base produces a salt and water.
Q24Past Paper · PPSC/FPSC/NTSmedium
A salt formed from a strong acid and a strong base is
1. AAcidic
2. BBasic
3. CAmphoteric
4. DNeutral
💡 Explanation:
Neither ion hydrolyzes significantly, so the resulting salt solution remains neutral.
Q25medium
A salt formed from a strong acid and a weak base is
1. ABasic
2. BNeutral
3. CAcidic
4. DAmphoteric
💡 Explanation:
The conjugate acid of the weak base hydrolyzes in water, making the solution acidic.
Q26medium
A salt formed from a weak acid and a strong base is
1. AAcidic
2. BBasic
3. CNeutral
4. DAmphoteric
💡 Explanation:
The conjugate base of the weak acid hydrolyzes in water, making the solution basic.
Q27Past Paper · PPSC/FPSC/NTSmedium
An amphoteric substance is one that can act as
1. AOnly an acid
2. BOnly a base
3. CNeither an acid nor a base
4. DBoth an acid and a base
💡 Explanation:
Amphoteric substances can donate or accept protons, behaving as either an acid or a base.
Q28medium
Which of the following oxides is amphoteric
1. ANa2O
2. BCO2
3. CAl2O3
4. DSO3
💡 Explanation:
Aluminum oxide reacts with both acids and bases, making it amphoteric.
Q29medium
A buffer solution resists changes in
1. AVolume
2. BColor
3. CTemperature
4. DpH upon addition of small amounts of acid or base
💡 Explanation:
Buffer solutions maintain a nearly constant pH despite small additions of acid or base.
Q30Past Paper · PPSC/FPSC/NTSmedium
An acidic buffer is typically prepared from
1. AA strong acid and its salt
2. BA strong base and its salt
3. CTwo strong acids
4. DA weak acid and its conjugate base (salt)
💡 Explanation:
Acidic buffers combine a weak acid with a salt of its conjugate base to resist pH changes.
Q31medium
A basic buffer is typically prepared from
1. AA strong base and a strong acid
2. BA weak base and its conjugate acid (salt)
3. CTwo weak acids
4. DPure water
💡 Explanation:
Basic buffers combine a weak base with a salt of its conjugate acid.
Q32Past Paper · PPSC/FPSC/NTSmedium
Phenolphthalein indicator turns pink in
1. AAcidic solutions
2. BNeutral solutions
3. CBasic solutions
4. DAll solutions equally
💡 Explanation:
Phenolphthalein remains colorless in acid and neutral solutions but turns pink in basic conditions.
Q33medium
Methyl orange indicator turns red in
1. ABasic solutions
2. BNeutral solutions
3. CAcidic solutions
4. DAll solutions equally
💡 Explanation:
Methyl orange turns red in strongly acidic solutions and yellow in basic ones.
Q34medium
The process of adding an acid to a base (or vice versa) until the reaction is complete is called
1. ATitration
2. BDistillation
3. CFiltration
4. DSublimation
💡 Explanation:
Titration is the controlled addition of one reactant to another to determine reaction completion.
Q35Past Paper · PPSC/FPSC/NTSmedium
The point in a titration where equal moles of acid and base have reacted is called the
1. ApH point
2. BBuffer point
3. CEquivalence point
4. DBoiling point
💡 Explanation:
The equivalence point marks where stoichiometrically equal amounts of acid and base have reacted.
Q36medium
Table salt (sodium chloride) is chemically classified as
1. AAn acid
2. BA neutral salt
3. CA base
4. DAn oxide
💡 Explanation:
Sodium chloride, formed from a strong acid and strong base, is a neutral salt.
Q37medium
Baking soda (sodium bicarbonate) reacts with acids to release
1. ACarbon dioxide gas
2. BHydrogen gas
3. COxygen gas
4. DNitrogen gas
💡 Explanation:
Sodium bicarbonate reacts with acids to produce carbon dioxide, water, and a salt.
Q38Past Paper · PPSC/FPSC/NTSmedium
Antacid tablets relieve acidity in the stomach because they contain
1. AStrong acids
2. BSugar only
3. CNeutral salts
4. DMild bases such as magnesium or aluminum hydroxide
💡 Explanation:
Antacids neutralize excess stomach acid using mild, safe bases.
Q39medium
The strength of an acid is measured quantitatively by its
1. AMolar mass
2. BBoiling point
3. CDissociation (ionization) constant, Ka
4. DColor intensity
💡 Explanation:
Ka quantifies how completely an acid dissociates in water, indicating its strength.
Q40medium
A higher Ka value indicates a
1. AStronger acid
2. BWeaker acid
3. CNeutral solution
4. DBasic solution
💡 Explanation:
A larger Ka value means greater dissociation, corresponding to a stronger acid.
Q41Past Paper · PPSC/FPSC/NTShard
pOH is related to pH by the equation
1. ApH + pOH = 14
2. BpH − pOH = 14
3. CpH × pOH = 14
4. DpH = pOH always
💡 Explanation:
At 25°C, pH and pOH always sum to 14 due to the water ionization constant.
Q42hard
If a solution has a pH of 3, its pOH is
1. A11
2. B3
3. C7
4. D14
💡 Explanation:
Since pH + pOH = 14, a pH of 3 gives a pOH of 11.
Q43hard
Universal indicator is used to
1. AMeasure temperature
2. BEstimate the approximate pH of a solution using a color chart
3. CMeasure the molar mass
4. DDetect the presence of metals only
💡 Explanation:
Universal indicator changes through a range of colors corresponding to different pH values.
Q44Past Paper · PPSC/FPSC/NTShard
Which of the following acids is found in vinegar
1. ACitric acid
2. BFormic acid
3. CLactic acid
4. DAcetic acid
💡 Explanation:
Vinegar's sour taste and properties come from dissolved acetic acid.
Q45hard
Which acid is found in citrus fruits like lemons
1. ACitric acid
2. BAcetic acid
3. COxalic acid
4. DTartaric acid
💡 Explanation:
Citric acid is the primary organic acid responsible for the tartness of citrus fruits.
Q46hard
Which acid is present in the human stomach and aids digestion
1. ASulfuric acid
2. BNitric acid
3. CHydrochloric acid
4. DAcetic acid
💡 Explanation:
The stomach secretes hydrochloric acid to aid digestion and kill pathogens.
Q47Past Paper · PPSC/FPSC/NTShard
The salt formed when hydrochloric acid reacts with sodium hydroxide is
1. ASodium chloride
2. BSodium sulfate
3. CSodium nitrate
4. DSodium carbonate
💡 Explanation:
Neutralization of HCl with NaOH produces sodium chloride and water.
Q48hard
Which of the following best describes a normal salt
1. AContains replaceable H+ or OH- ions
2. BFormed from incomplete neutralization
3. CAlways acidic
4. DFormed by the complete neutralization of an acid and base with no replaceable H or OH
💡 Explanation:
A normal salt results from complete neutralization, leaving no acidic hydrogen or basic hydroxide.
Q49hard
An acid salt contains a replaceable
1. AMetal ion
2. BHydrogen atom
3. CHydroxide ion only
4. DOxide ion
💡 Explanation:
Acid salts retain at least one ionizable hydrogen atom from the parent acid.
Q50hard
Which of the following is an example of an acid salt
1. ANaCl
2. BNa2CO3
3. CNaHCO3
4. DCaCO3
💡 Explanation:
Sodium bicarbonate retains one replaceable hydrogen atom, making it an acid salt.
Q51medium
Litmus paper turns ___ in basic solutions
1. ARed
2. BColorless
3. CYellow
4. DBlue
💡 Explanation:
Bases turn red litmus paper blue, a classic acid-base indicator test.
Q52medium
Litmus paper turns ___ in acidic solutions
1. ABlue
2. BGreen
3. CColorless
4. DRed
💡 Explanation:
Acids turn blue litmus paper red, a classic acid-base indicator test.

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Acids, Bases and Salts MCQs 2026

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