中文（繁體）
中文（简体）
English
S2 Science: Acids, Alkalis and Neutralisation (Paper 1 (basics))
← Back to the Secondary Science chapter index
S2 Science: Acids, Alkalis and Neutralisation (Paper 1 (basics))
This paper starts from the basic properties of acids and alkalis: litmus colours, reading pH values and the products of neutralisation, then adds dilution and neutralisation volume calculations.
Direct answers For every question, first decide whether the solution is acidic, neutral or alkaline, then choose the indicator colour or the calculation; never multiply blindly. The key words are acid, alkali, neutralisation and dilution, and each one tells you which rule applies.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 20 |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1 |
| Chapter | Chapter: S2 Science: Acids, Alkalis and Neutralisation |
| Level | S2 |
02 Questions (10 items)
- FoundationWhat colour does blue litmus paper turn in an acidic solution?
- FoundationA solution has a pH of 7. Which type is it?
- FoundationWhat colour does red litmus paper turn in sodium hydroxide solution?
- IntermediateLemon juice has a pH of about 2. Is it acidic, neutral or alkaline?
- IntermediateWhen hydrochloric acid is fully neutralised by sodium hydroxide solution, what is formed besides water?
- IntermediateWhat colour is phenolphthalein in an acidic solution?
- ChallengeHow many times greater is the hydrogen ion concentration at pH 3 than at pH 6?
- ChallengeFive cm³ of acid is added to 50 cm³ of water, giving 55 cm³. The concentration becomes what fraction of the original?
- ChallengeWhat volume of 0.10 mol/dm³ sodium hydroxide is needed to neutralise 25.0 cm³ of 0.10 mol/dm³ hydrochloric acid?
- Error redoA student thinks a larger pH means a stronger acid. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Red | Acidic solutions turn blue litmus red, which is one shared property of acids. |
| 2 | Neutral | A pH below 7 is acidic, above 7 is alkaline, and 7 is neutral, as in pure water. |
| 3 | Blue | Alkaline solutions turn red litmus blue, the opposite of what acids do. |
| 4 | Acidic, and fairly strongly so | A pH of 2 is below 7, and the smaller the value the more acidic the solution. |
| 5 | A salt, namely sodium chloride | An acid plus an alkali gives a salt and water, and this reaction is called neutralisation. |
| 6 | Colourless | Phenolphthalein is colourless in acidic and neutral solutions and turns pink only in alkali. |
| 7 | One thousand times | Each pH unit means a tenfold change, so three units give ten to the power three. |
| 8 | One eleventh | The dilution factor is the total volume divided by the acid volume, 55 over 5, which is 11. |
| 9 | 25.0 cm³ | The mole ratio is one to one, so equal concentrations need equal volumes. |
| 10 | It is the other way round: a smaller pH means a stronger acid, so pH 2 is more acidic than pH 5 | The pH scale runs from 0 to 14, with the acidic end near 0, the alkaline end near 14 and 7 as neutral. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
For acid and alkali questions ask three things: is the solution acidic or alkaline, what colour was the indicator, and what is the mole ratio in the neutralisation.Tutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.