ScienceAges 13-15

Acids, bases & the pH scale

Use the 0–14 pH scale, indicators and neutralisation reactions to classify acidic, neutral and alkaline solutions. Review suitability for your learners before teaching.

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Worksheet StudioPractice pack · Ages 13-15

Acids, bases & the pH scale

Take your time. Show your thinking.

1. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
2. Does an acidic solution (such as lemon juice or hydrochloric acid) have a pH less than 7 or greater than 7?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
3. Which gas is produced when a metal carbonate (such as calcium carbonate) reacts with an acid: carbon dioxide or nitrogen?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
4. What is the difference between a strong acid (like HCl) and a weak acid (like ethanoic acid) in water: a strong acid fully ionises (dissociates), whereas a weak acid only partially ionises, or a strong acid has pH 12?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
5. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
6. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
7. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
8. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
9. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
10. What colour does Universal Indicator turn in a neutral solution of pH 7: green or red?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
11. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

12 questions · Seed 104739 · Age guidance, not curriculum certification

View the answer key

Worksheet StudioAnswer key · Ages 13-15

Acids, bases & the pH scale

Answers and reasoning. Review before teaching.

1. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
Sulfate
Sulfuric acid forms sulfate salts; nitric acid forms nitrates; hydrochloric acid forms chlorides.
2. Does an acidic solution (such as lemon juice or hydrochloric acid) have a pH less than 7 or greater than 7?
Less than 7
Acids have pH values below 7; the lower the pH, the stronger or more concentrated the acid.
3. Which gas is produced when a metal carbonate (such as calcium carbonate) reacts with an acid: carbon dioxide or nitrogen?
Carbon dioxide
Acid + Carbonate → Salt + Water + Carbon dioxide (which turns limewater milky).
4. What is the difference between a strong acid (like HCl) and a weak acid (like ethanoic acid) in water: a strong acid fully ionises (dissociates), whereas a weak acid only partially ionises, or a strong acid has pH 12?
A strong acid fully ionises (dissociates), whereas a weak acid only partially ionises
Acid strength refers to the degree of ionisation in water.
5. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
Sodium chloride
HCl + NaOH → NaCl (sodium chloride) + H₂O.
6. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
Burette
A burette delivers variable volumes accurately to within 0.05 cm³.
7. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
Citric acid
Citrus fruits contain citric acid.
8. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
10
pH = −log₁₀[H⁺], so each whole unit decrease represents a tenfold increase in [H⁺].
9. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
A salt and water
Acid + Alkali → Salt + Water (H⁺ + OH⁻ → H₂O).
10. What colour does Universal Indicator turn in a neutral solution of pH 7: green or red?
Green
Universal Indicator is green at neutral pH 7, red in strong acid, and purple in strong alkali.
11. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
Colourless in acid and pink in alkali
Phenolphthalein is colourless below pH 8.2 and turns pink-magenta in alkaline solutions.
12. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
Red
Acids turn blue litmus paper red.

12 questions · Seed 104739 · Age guidance, not curriculum certification

Worksheet StudioPractice pack · Ages 13-15

Acids, bases & the pH scale

Take your time. Show your thinking.

1. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
2. Does an acidic solution (such as lemon juice or hydrochloric acid) have a pH less than 7 or greater than 7?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
3. Which gas is produced when a metal carbonate (such as calcium carbonate) reacts with an acid: carbon dioxide or nitrogen?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
4. What is the difference between a strong acid (like HCl) and a weak acid (like ethanoic acid) in water: a strong acid fully ionises (dissociates), whereas a weak acid only partially ionises, or a strong acid has pH 12?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
5. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
6. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
7. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
8. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
9. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
10. What colour does Universal Indicator turn in a neutral solution of pH 7: green or red?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
11. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution
12. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
pH Scale: 0 (Acid) → 7 → 14 (Alkali) · Indicator Solution

12 questions · Seed 104739 · Age guidance, not curriculum certification

Worksheet StudioAnswer key · Ages 13-15

Acids, bases & the pH scale

Answers and reasoning. Review before teaching.

1. Which type of salt is always produced by reactions of sulfuric acid (H₂SO₄): a sulfate or a nitrate?
Sulfate
Sulfuric acid forms sulfate salts; nitric acid forms nitrates; hydrochloric acid forms chlorides.
2. Does an acidic solution (such as lemon juice or hydrochloric acid) have a pH less than 7 or greater than 7?
Less than 7
Acids have pH values below 7; the lower the pH, the stronger or more concentrated the acid.
3. Which gas is produced when a metal carbonate (such as calcium carbonate) reacts with an acid: carbon dioxide or nitrogen?
Carbon dioxide
Acid + Carbonate → Salt + Water + Carbon dioxide (which turns limewater milky).
4. What is the difference between a strong acid (like HCl) and a weak acid (like ethanoic acid) in water: a strong acid fully ionises (dissociates), whereas a weak acid only partially ionises, or a strong acid has pH 12?
A strong acid fully ionises (dissociates), whereas a weak acid only partially ionises
Acid strength refers to the degree of ionisation in water.
5. Which salt is formed when hydrochloric acid (HCl) is neutralised by sodium hydroxide (NaOH): sodium chloride or sodium sulfate?
Sodium chloride
HCl + NaOH → NaCl (sodium chloride) + H₂O.
6. In an acid–base titration, which piece of graduated glassware with a tap at the bottom is used to measure the exact volume of acid or alkali added: a burette or a beaker?
Burette
A burette delivers variable volumes accurately to within 0.05 cm³.
7. What weak organic acid is found naturally in lemons, limes and oranges: citric acid or sulfuric acid?
Citric acid
Citrus fruits contain citric acid.
8. Because the pH scale is logarithmic, a decrease of 1 pH unit (e.g. from pH 4 to pH 3) means the H⁺ ion concentration increases by a factor of: 10 or 2?
10
pH = −log₁₀[H⁺], so each whole unit decrease represents a tenfold increase in [H⁺].
9. What are the two products formed when an acid reacts with an alkali in a neutralisation reaction: a salt and water, or hydrogen and carbon?
A salt and water
Acid + Alkali → Salt + Water (H⁺ + OH⁻ → H₂O).
10. What colour does Universal Indicator turn in a neutral solution of pH 7: green or red?
Green
Universal Indicator is green at neutral pH 7, red in strong acid, and purple in strong alkali.
11. What colour is phenolphthalein indicator in an acidic solution vs a basic solution: colourless in acid and pink in alkali, or blue in both?
Colourless in acid and pink in alkali
Phenolphthalein is colourless below pH 8.2 and turns pink-magenta in alkaline solutions.
12. What colour does blue litmus paper turn when dipped into an acidic solution: red or blue?
Red
Acids turn blue litmus paper red.

12 questions · Seed 104739 · Age guidance, not curriculum certification