GCE A-Level (Singapore) Acid-Base Equilibria — practice questions — page 3

Explore 65 free Acid-Base Equilibria questions in GCE A-Level (Singapore) Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Acid-Base Equilibria questions and exercises with answers

Showing questions 61–65 of 65.

Over what pH range does methyl orange complete its colour change?Read the answer and worked solution →Line up three acids or three basesRead the answer and worked solution →Match each acid to its conjugate baseRead the answer and worked solution →Tap the stronger acid each timeRead the answer and worked solution →Sort species into donor and acceptorRead the answer and worked solution →

Worked practice questions

Over what pH range does methyl orange complete its colour change?

From 1.1 up to 2.4 on the pH scale
From 4.4 up to 6.1 on the pH scale
From 8.3 up to 10.0 on the pH scale
From 3.1 up to 4.4 on the pH scale

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Correct answer: D. From 3.1 up to 4.4 on the pH scale

1. Methyl orange is a weak acid whose two forms differ in colour. 2. Its undissociated form is red and its anion is yellow. 3. At a hydronium concentration of 8 x 10^-4 M, a pH of 3.1, the solution appears red. 4. At 4 x 10^-5 M, a pH of 4.4, most of the indicator is in the yellow form. 5. So the colour change interval runs from pH 3.1 to pH 4.4. 6. Beyond those limits further change in pH produces no visible difference. _Source: OpenStax Chemistry (CC BY 4.0), Ch 14 "Acid-Base Equilibria", section 14.7 Acid-Base Titrations_

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Line up three acids or three bases

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Grid

1. Group
  Strong acid
  Item
  HCl
2. Group
  Weak acid
  Item
  HF
3. Group
  Strong acid
  Item
  HNO3
1. Group
  Strong base
  Item
  NaOH
2. Group
  Strong acid
  Item
  HBr
3. Group
  Strong base
  Item
  KOH
1. Group
  Weak acid
  Item
  HNO2
2. Group
  Weak acid
  Item
  HCN
3. Group
  Strong base
  Item
  LiOH

Groups

Item
Strong acid
Item
Weak acid
Item
Strong base

Instructions

Swap two neighbouring tiles to line up three strong acids, weak acids or strong bases.

_Source: OpenStax Chemistry, Ch 14 Acid-Base Equilibria, section The Relative Strengths of Strong Acids and Bases_

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Match each acid to its conjugate base

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Matching pairs

A
HF
B
F-
A
H2SO4
B
HSO4-
A
NH4+
B
NH3
A
HNO2
B
NO2-
A
HCN
B
CN-
A
H2O
B
OH-

Instructions

Flip two cards to pair an acid with the conjugate base left behind when it loses a proton.

_Source: OpenStax Chemistry, Ch 14 Acid-Base Equilibria, section 14.1 Brønsted-Lowry Acids and Bases_