Acids and Bases Quiz Answers and Explanations

Acids and Bases Quiz

20 Questions

With Answers and Explanations

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What is the pH range for acids?

  1. 0-7
  2. 7-14
  3. 7 only
  4. 14 only

Answer: a) 0-7

Explanation: Acids have a pH below 7 on the pH scale, which ranges from 0 to 14. The lower the pH, the stronger the acid.

Which of the following is a characteristic of bases?

  1. Sour taste
  2. Slippery feel
  3. React with metals to produce hydrogen gas
  4. Turn blue litmus paper red

Answer: b) Slippery feel

Explanation: Bases typically have a slippery or soapy feel when touched. They also taste bitter (not sour), turn red litmus paper blue, and don’t react with metals to produce hydrogen gas.

What is the chemical formula for hydrochloric acid?

  1. H₂SO₄
  2. HNO₃
  3. HCl
  4. CH₃COOH

Answer: c) HCl

Explanation: Hydrochloric acid has the chemical formula HCl. It consists of one hydrogen atom bonded to one chlorine atom.

Which of these is an Arrhenius base?

  1. NH₃
  2. NaOH
  3. CH₃COOH
  4. HCl

Answer: b) NaOH

Explanation: Sodium hydroxide (NaOH) is an Arrhenius base because it dissociates in water to produce hydroxide (OH⁻) ions.

What happens when an acid and a base react?

  1. Combustion
  2. Decomposition
  3. Neutralization
  4. Oxidation

Answer: c) Neutralization

Explanation: When an acid and a base react, they undergo a neutralization reaction, producing water and a salt.

Which of the following is an example of an amphiprotic substance?

  1. HCl
  2. NaOH
  3. H₂O
  4. NaCl

Answer: c) H₂O

Explanation: Water (H₂O) is amphiprotic, meaning it can act as both an acid and a base by donating or accepting protons.

What is the pH of a neutral solution?

  1. 0
  2. 7
  3. 14
  4. 1

Answer: b) 7

Explanation: A neutral solution has a pH of 7, which is the midpoint of the pH scale.

Which scientist proposed the Brønsted-Lowry theory of acids and bases?

  1. Svante Arrhenius
  2. Gilbert Lewis
  3. Johannes Brønsted and Thomas Lowry
  4. Antoine Lavoisier

Answer: c) Johannes Brønsted and Thomas Lowry

Explanation: The Brønsted-Lowry theory, which defines acids as proton donors and bases as proton acceptors, was independently proposed by Johannes Brønsted and Thomas Lowry in 1923.

What is the conjugate base of HCO₃⁻ ?

  1. H₂CO₃
  2. CO₃²⁻
  3. OH⁻
  4. H⁺

Answer: b) CO₃²⁻

Explanation: The conjugate base is formed by removing one proton (H⁺) from the acid. Therefore, the conjugate base of HCO₃⁻ is CO₃²⁻.

Which of the following is a strong base?

  1. NH₃
  2. CH₃NH₂
  3. KOH
  4. C₆H₅NH₂

Answer: c) KOH

Explanation: Potassium hydroxide (KOH) is a strong base because it completely dissociates in water, releasing all of its hydroxide ions.

What is the pOH of a solution with a pH of 4?

  1. 4
  2. 7
  3. 10
  4. 14

Answer: c) 10

Explanation: The sum of pH and pOH is always 14 in aqueous solutions. Therefore, if pH = 4, then pOH = 14 – 4 = 10.

Which indicator turns red in acidic solutions?

  1. Phenolphthalein
  2. Methyl orange
  3. Bromothymol blue
  4. Litmus

Answer: b) Methyl orange

Explanation: Methyl orange turns red in acidic solutions, while it appears yellow in basic solutions.

What is the Lewis definition of a base?

  1. Proton acceptor
  2. Electron pair donor
  3. Hydroxide ion donor
  4. Proton donor

Answer: b) Electron pair donor

Explanation: According to the Lewis theory, a base is defined as an electron pair donor.

Which of the following acids is diprotic?

  1. HCl
  2. H₂SO₄
  3. HNO₃
  4. CH₃COOH

Answer: b) H₂SO₄

Explanation: Sulfuric acid (H₂SO₄) is diprotic, meaning it can donate two protons per molecule in an acid-base reaction.

What is the name of the process by which water ionizes?

  1. Hydration
  2. Dehydration
  3. Auto-ionization
  4. Neutralization

Answer: c) Auto-ionization

Explanation: The process by which water molecules react with each other to produce hydronium (H₃O⁺) and hydroxide (OH⁻) ions is called auto-ionization or self-ionization.

Which of these is not a property of acids?

  1. React with metals to produce hydrogen gas
  2. Turn blue litmus paper red
  3. Conduct electricity when dissolved in water
  4. Feel slippery to the touch

Answer: d) Feel slippery to the touch

Explanation: Feeling slippery to the touch is a characteristic of bases, not acids. Acids typically have a sour taste and do not feel slippery.

What is the hydroxide ion concentration in a solution with a pH of 3?

  1. 10⁻³ M
  2. 10⁻¹¹ M
  3. 3 M
  4. 10⁻¹⁴ M

Answer: b) 10⁻¹¹ M

Explanation: In an aqueous solution, pH + pOH = 14. If pH = 3, then pOH = 11. The hydroxide ion concentration is 10⁻ᵖᴼᴴ, so [OH⁻] = 10⁻¹¹ M.

Which acid is commonly known as vitamin C?

  1. Citric acid
  2. Ascorbic acid
  3. Acetic acid
  4. Carbonic acid

Answer: b) Ascorbic acid

Explanation: Ascorbic acid is the chemical name for vitamin C, an essential nutrient for humans.

What is the conjugate acid of PO₄³⁻ ?

  1. H₃PO₄
  2. H₂PO₄⁻
  3. HPO₄²⁻
  4. P₂O₅

Answer: c) HPO₄²⁻

Explanation: The conjugate acid is formed by adding one proton (H⁺) to the base. Therefore, the conjugate acid of PO₄³⁻ is HPO₄²⁻.

Which of the following is an application of a buffer solution?

  1. Cleaning windows
  2. Generating electricity
  3. Maintaining blood pH
  4. Bleaching clothes

Answer: c) Maintaining blood pH

Explanation: Buffer solutions are used to maintain a relatively constant pH in biological systems, such as blood, where maintaining a stable pH is crucial for proper functioning.

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