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S5 Chemistry: Alcohols, Carboxylic Acids and Esters (Paper 2: Intermediate)
S5 Chemistry: Alcohols, Carboxylic Acids and Esters (Paper 2: Intermediate)
Ten items on oxidation, dehydration, acid tests and hydrolysis, with gas volume and yield calculations.
Direct answers Answers in order: green, ethene, bubbles, 0.60 dm3, 92 g, methyl butanoate, sodium ethanoate and ethanol, the acid is weak, about 69.9%, sodium ethanoate and ethanol.
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: S5 Chemistry: Alcohols, Carboxylic Acids and Esters |
| Level | S5 |
02 Questions (10 items)
- FoundationEthanol is warmed with acidified potassium dichromate solution. What colour change is seen?
- FoundationEthanol is heated with concentrated sulphuric acid at 170 degrees Celsius. What is the main product?
- FoundationEthanoic acid is added to sodium carbonate solution. What is observed?
- Intermediate0.050 mol of ethanoic acid reacts with excess sodium carbonate. What volume of carbon dioxide forms? (24 dm3)
- Intermediate180 g of glucose is fully fermented. What mass of ethanol should form?
- IntermediateButanoic acid reacts with methanol. What is the ester called?
- ChallengeEthyl ethanoate is heated with sodium hydroxide solution. What forms?
- ChallengeA 0.10 mol/dm3 ethanoic acid solution has pH about 3, while hydrochloric acid of the same concentration has pH about 1. Why?
- ChallengeThe theoretical yield is 17.6 g but only 12.3 g is obtained. What is the percentage yield?
- Error redoError replay: a student heats ethanol, ethanoic acid and sodium hydroxide together to make an ester. What is actually obtained?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Orange turns green | Dichromate ions are reduced to chromium three ions, so the colour turns green as ethanol is oxidised. |
| 2 | Ethene, by dehydration | The acid removes water from ethanol and a double bond forms; at lower temperature an ether is favoured. |
| 3 | Bubbles of carbon dioxide | An acid with a carbonate releases carbon dioxide, a simple test that separates acids from alcohols. |
| 4 | 0.60 dm3 | Two moles of acid release one mole of gas, so 0.025 mol times 24 gives the volume. |
| 5 | 92 g | 180 g is one mole of glucose, which gives two moles of ethanol at 46 g each. |
| 6 | Methyl butanoate | The alcohol part comes first in the name, so methanol gives the methyl prefix. |
| 7 | Sodium ethanoate and ethanol | Alkaline hydrolysis goes to completion and gives the salt of the acid, not the acid itself. |
| 8 | Ethanoic acid is weak and only partly ionised | Most ethanoic acid molecules keep their hydrogen, so the hydrogen ion concentration is far lower. |
| 9 | About 69.9% | Divide the actual mass by the theoretical mass and multiply by one hundred. |
| 10 | Sodium ethanoate and ethanol, because the ester is hydrolysed | Sodium hydroxide is a base and hydrolyses any ester formed, so concentrated sulphuric acid is used instead. |
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.
Keep oxidation, dehydration and esterification apart; the conditions decide the product.Tutor Registration →
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