Quick questions on Alcohols and carboxylic acids - WJEC A-Level Chemistry

Carboxylic acids are weak acids that release $\text{H}^+$ from the $\text{COOH}$ group. They react with reactive metals, carbonates (effervescence of $\text{CO}_2$, a test) and bases to form salts.

The key practical skill is controlling how far a primary alcohol is oxidised. Using a limited amount of oxidant and distilling the product off as it forms isolates the aldehyde, because removing it from the flask stops it being oxidised further. Refluxing with excess oxidant instead returns the vapour to the flask, so the aldehyde stays in contact with the oxidant and is oxidised all the way to the carboxylic acid. The same reagent therefore gives two different products depending purely on the apparatus and the amount of oxidant, a distinction examiners test directly.

Many fruity smells (ethyl ethanoate, pentyl ethanoate) are esters made by Fischer esterification, used in foods, perfumes and solvents. Biodiesel by transesterification. Vegetable-oil esters are converted to methyl esters (biodiesel), an industrial-scale ester reaction linked to the renewable-fuels theme of Unit 2's wider impact content.

State the colour change when a primary alcohol is oxidised by acidified potassium dichromate. [1 mark]

Name the ester formed from methanol and propanoic acid. [1 mark]

Give the reagents and conditions to dehydrate ethanol to ethene. [1 mark]

State how you would isolate an aldehyde rather than a carboxylic acid when oxidising a primary alcohol. [1 mark]

State the two roles of concentrated sulfuric acid in esterification. [2 marks]