中文（繁體）
中文（简体）
English
S5 Chemistry Titration and pH, Paper 1: neutralising volumes, dilution and titration means
S5 Chemistry Titration and pH, Paper 1: neutralising volumes, dilution and titration means
Ten graded items from one-to-one neutralisation through diprotic acids, dilution factors and titration readings, each with an answer.
Focus Discard wild titration readings before averaging; a diprotic acid releases two hydrogen ions; dilution keeps the moles constant.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S5 Chemistry: Acid-Base Titration and pH |
| Level | Four basic, three advanced, two challenge and one error-repair item |
02 Questions (10 items)
- FoundationWhat volume of 0.100 mol dm^-3 hydrochloric acid neutralises 25.0 cm^3 of 0.100 mol dm^-3 sodium hydroxide?
- FoundationWhat is the pH of 0.010 mol dm^-3 hydrochloric acid?
- FoundationWhat is the pH of 0.010 mol dm^-3 sodium hydroxide at 25 C?
- FoundationAt the end point of a titration, when does the indicator change colour?
- IntermediateWhat volume of 0.100 mol dm^-3 sulphuric acid neutralises 20.0 cm^3 of 0.150 mol dm^-3 sodium hydroxide?
- IntermediateWhat is the pH after 0.10 mol dm^-3 hydrochloric acid is diluted a hundredfold?
- IntermediateWhat is the pH of 0.0050 mol dm^-3 sulphuric acid, a fully ionised diprotic acid?
- Challenge25.0 cm^3 of hydrochloric acid of unknown concentration needs 22.30, 22.40 and 22.50 cm^3 of 0.100 mol dm^-3 sodium hydroxide. Find the acid concentration.
- ChallengeWhat volume of 0.100 mol dm^-3 hydrochloric acid reacts completely with 0.250 g of calcium carbonate of molar mass 100 g mol^-1?
- Error redoError repair: a student averages 24.10, 24.20 and 26.50 cm^3 to get 24.93 cm^3. What is the correct mean?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | 25.0 cm^3 | Sodium hydroxide and hydrochloric acid react one to one, so equal concentrations need equal volumes. |
| 2 | pH 2.00 | A strong acid ionises fully, so the hydrogen ion concentration is 0.010 and the pH is 2.00. |
| 3 | pH 12.00 | The hydroxide concentration is 0.010, so pOH is 2.00 and pH is 14 minus 2.00. |
| 4 | At the last drop of standard solution, when the pH changes sharply | The end point is the instant of exact neutralisation, when the indicator changes colour. |
| 5 | 15.0 cm^3 | There is 0.00300 mol of alkali; a diprotic acid needs half that, so 0.00150 mol divides by 0.100 to give 15.0 cm^3. |
| 6 | pH 3.00 | Diluting a hundredfold lowers the hydrogen ion concentration to 0.0010, so pH rises from 1.00 to 3.00. |
| 7 | pH 2.00 | Each molecule releases two hydrogen ions, giving 0.010, and the negative logarithm is 2.00. |
| 8 | 0.0896 mol dm^-3 | The three readings agree, averaging 22.40 cm^3 or 0.002240 mol, which divides by 0.0250 dm^3 to give 0.0896. |
| 9 | 50.0 cm^3 | 0.00250 mol of calcium carbonate needs 0.00500 mol of acid, which divides by 0.100 to give 0.0500 dm^3. |
| 10 | 24.15 cm^3 | The reading 26.50 is wild and must be discarded, so the mean of the other two is 24.15 cm^3. |
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.
Book an S5 Chemistry tutorTutor 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.
