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A-Level Chemistry (F324: Rings, Acids & Amines) Quiz on Chemical tests for carbonyl compounds, created by anndjan21 on 14/03/2016.

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Chemical tests for carbonyl compounds

Chemical tests for carbonyl compounds

Question 1 of 17

1

How do you identify a carbonyl compound?

Select one or more of the following:

  • Add Tollens' reagent

  • Add Biuret reagent

  • Add 2,4-DNPH

  • Add carboxylic acid

Explanation

Question 2 of 17

1

What is Brady's reagent?

Select one or more of the following:

  • A mixture of H2SO4 and benzene + 2,4-DNPH

  • A mixture of HCl and ethanol + 2,4-DNPH

  • A mixture of NaOH and methanol + 2,4-DNPH

  • A mixture of H2SO4 and methanol + 2,4-DNPH

Explanation

Question 3 of 17

1

What's formed when 2,4-DNPH is added to an aldehyde/ketone?

Select one or more of the following:

  • A blue solid

  • An orange/yellow precipiate

  • An orange/yellow solution

  • A green precipitate

Explanation

Question 4 of 17

1

What does the 2,4-DNPH derivative confirm?

Select one or more of the following:

  • The presence of C=O

  • The presence of COOH

  • The presence of OH

  • The presence of COO

Explanation

Question 5 of 17

1

What happens when 2,4-DNPH added to carboxylic acid/ester?

Select one or more of the following:

  • An orange/yellow precipitate formed

  • An orange to green colour change

  • A solid disappears

  • No precipitate formed

Explanation

Question 6 of 17

1

What is Tollen's reagent?

Select one or more of the following:

  • A weak oxidising agent

  • A weak reducing agent

  • A strong oxidising agent

  • A strong reducing agent

Explanation

Question 7 of 17

1

What happens to aldehydes when Tollens' reagent is added to it?

Select one or more of the following:

  • Oxidised to ketones

  • Reduced to carboxylic acids

  • Oxidised to carboxylic acids

  • Reduced to alcohols

Explanation

Question 8 of 17

1

What observation do you see when Tollen's reagent is added to an aldehyde?

Select one or more of the following:

  • Brown precipitate

  • Silver mirror

  • No observation

  • Brick red precipitate

Explanation

Question 9 of 17

1

Why is a silver mirror formed?

Select one or more of the following:

  • Al ions oxidised to Al metal

  • Silver ions reduced to silver metal

  • Silver ions oxidised to silver metal

  • Al ions reduced to Al metal

Explanation

Question 10 of 17

1

What is the equation for the silver mirror being formed?

Select one or more of the following:

  • Ag-(aq) + e+ ---> Ag(s)

  • Ag+(aq) ---> Ag(s) + e-

  • Ag+(s) + e- ---> Ag(aq)

  • Ag+(aq) + e- ---> Ag(s)

Explanation

Question 11 of 17

1

What observation do you see when Tollen's added to ketone?

Select one or more of the following:

  • No observation

  • Silver mirror

  • Deep blue solution

  • Orange to green colour change

Explanation

Question 12 of 17

1

What's the reason for no observation?

Select one or more of the following:

  • The reaction is too slow

  • Ketones are not reduced by Tollens' reagent

  • Ketones are not oxidised by Tollens' reagent

  • Ketones are just dead

Explanation

Question 13 of 17

1

What's the oxidising species in Tollens' reagent?

Select one or more of the following:

  • Ag(aq)

  • Br+(aq)

  • Ag(s)

  • Ag+(aq)

Explanation

Question 14 of 17

1

What conditions are required for these reactions?

Select one or more of the following:

  • Warm

  • Reflux

  • conc H2SO4

  • Alkaline

Explanation

Question 15 of 17

1

Fill the blank spaces to complete the text.

Filter and product. Measure of purified product which is very . Compare the melting point to a or to identify the unknown product and therefore the carbonyl compound.

Explanation

Question 16 of 17

1

Why does the yellow/orange solid have to be recrystallised?

Select one or more of the following:

  • Because it needs to be crystallised again

  • Because its slightly impure

  • Because it's fun

  • Because it needs to be more solid

Explanation

Question 17 of 17

1

Why can't boiling points be used to distinguish between aldehydes and ketones?

Select one or more of the following:

  • It's not possible to know all of the boiling points for every single one

  • It will all boil away

  • Some are very close together/similar

  • It's not accurate enough

Explanation

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