Alcohols and Carboxylic Acids

What Alcohols and Carboxylic Acids covers

Alcohols and Carboxylic Acids is examined on AS Unit 2 of WJEC Chemistry, Energy, Rate and Chemistry of Carbon Compounds. 155 recall questions across 11 subtopics.

The 11 subtopics

Each one has its own page. WJEC AS Chemistry students sit this topic in the first year.

• Two routes to ethanol: hydration and fermentation — hydration of etheneRecall questions on hydration and fermentation — hydration of ethene.Open →
• Two routes to ethanol: hydration and fermentation — fermentationRecall questions on hydration and fermentation — fermentation.Open →
• Two routes to ethanol: hydration and fermentation — comparing the two routes on rateRecall questions on hydration and fermentation — comparing the two routes on rate.Open →
• Classifying alcohols and dehydrating themRecall questions on Classifying alcohols and dehydrating them.Open →
• Oxidising alcohols to aldehydes, ketones and acidsRecall questions on Oxidising alcohols to aldehydes, ketones and acids.Open →
• Chemical tests for alcohols and carboxylic acidsEighteen recall questions on chemical tests for alcohols and carboxylic acids.Open →
• Carboxylic acids, bases and saltsRecall questions on Carboxylic acids, bases and salts.Open →
• Making an ester and separating it by distillation: esterificationRecall questions on esterification.Open →
• Making an ester and separating it by distillation: carrying out the preparationEight recall questions on making an ester and separating it by distillation: carrying out the preparation.Open →
• Making an ester and separating it by distillation: separating and purifyingRecall questions on separating and purifying.Open →
• Making an ester and separating it by distillation: yieldRecall questions on difference between simple and fractional distillation.Open →

What you need to know

Answer each one before you reveal it.

Take Alcohols and Carboxylic Acids further

The same content, four other ways.

Questions from this topic

Each one with the model answer underneath.

1. 1

   How is ethanol manufactured from ethene?

   Model answer

   Ethene is hydrated by steam in a reversible addition reaction, C₂H₄(g) + H₂O(g) ⇌ C₂H₅OH(g). The water molecule adds across the double bond, so no other product is formed.

2. 2

   What conditions are used for the industrial hydration of ethene?

   Model answer

   A temperature of about 300 °C, a pressure of about 60–70 atmospheres, and a catalyst of phosphoric(V) acid adsorbed on solid silica.

3. 3

   What does the phosphoric(V) acid do in the hydration of ethene?

   Model answer

   It catalyses the reaction, providing an alternative route of lower activation energy so that equilibrium is reached faster. It is not used up, and it does not change the position of the equilibrium or the final yield.

4. 4

   Only about 5% of the ethene is converted to ethanol on each pass through the reactor. Why is the process still economic?

   Model answer

   The ethanol is condensed out and the unreacted ethene and steam are recycled back through the reactor. Repeated passes raise the overall conversion to roughly 95%, so very little ethene is wasted.

5. 5

   The hydration of ethene is exothermic. Explain why a temperature as high as 300 °C is used even though this lowers the equilibrium yield.

   Model answer

   For an exothermic reaction, raising the temperature shifts the equilibrium to the left and reduces the yield, but it also increases the rate. At a low temperature the yield would be high but the reaction would be far too slow to be profitable, so 300 °C is a compromise between yield and rate.

6. 6

   Use Le Chatelier's principle to explain why a high pressure favours the formation of ethanol from ethene and steam.

   Model answer

   There are two moles of gas on the left of C₂H₄(g) + H₂O(g) ⇌ C₂H₅OH(g) and only one on the right. Raising the pressure shifts the equilibrium towards the side with fewer gas molecules, which is the ethanol side, so the equilibrium yield rises.

What is inside Levo

Six ways to work the same material.

Alcohols and Carboxylic Acids revision questions

Is Alcohols and Carboxylic Acids examined at AS in WJEC Chemistry?

Yes. It sits in AS Unit 2, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.

What does Alcohols and Carboxylic Acids cover in WJEC AS-Level Chemistry?

11 subtopics: two routes to ethanol: hydration and fermentation — hydration of ethene, two routes to ethanol: hydration and fermentation — fermentation, two routes to ethanol: hydration and fermentation — comparing the two routes on rate, classifying alcohols and dehydrating them, oxidising alcohols to aldehydes, ketones and acids, chemical tests for alcohols and carboxylic acids, carboxylic acids, bases and salts, making an ester and separating it by distillation: esterification, making an ester and separating it by distillation: carrying out the preparation, making an ester and separating it by distillation: separating and purifying and making an ester and separating it by distillation: yield. Each one has its own page with questions and model answers.

How is Alcohols and Carboxylic Acids organised?

By the WJEC 1410QS specification, subtopic by subtopic, so it matches the order you are taught it in.