4852752
Question 1
Question
How do you identify a carbonyl compound?
Answer
-
Add Tollens' reagent
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Add Biuret reagent
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Add 2,4-DNPH
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Add carboxylic acid
Question 2
Question
What is Brady's reagent?
Answer
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A mixture of H2SO4 and benzene + 2,4-DNPH
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A mixture of HCl and ethanol + 2,4-DNPH
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A mixture of NaOH and methanol + 2,4-DNPH
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A mixture of H2SO4 and methanol + 2,4-DNPH
Question 3
Question
What's formed when 2,4-DNPH is added to an aldehyde/ketone?
Answer
-
A blue solid
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An orange/yellow precipiate
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An orange/yellow solution
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A green precipitate
Question 4
Question
What does the 2,4-DNPH derivative confirm?
Answer
-
The presence of C=O
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The presence of COOH
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The presence of OH
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The presence of COO
Question 5
Question
What happens when 2,4-DNPH added to carboxylic acid/ester?
Answer
-
An orange/yellow precipitate formed
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An orange to green colour change
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A solid disappears
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No precipitate formed
Question 6
Question
What is Tollen's reagent?
Answer
-
A weak oxidising agent
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A weak reducing agent
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A strong oxidising agent
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A strong reducing agent
Question 7
Question
What happens to aldehydes when Tollens' reagent is added to it?
Answer
-
Oxidised to ketones
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Reduced to carboxylic acids
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Oxidised to carboxylic acids
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Reduced to alcohols
Question 8
Question
What observation do you see when Tollen's reagent is added to an aldehyde?
Answer
-
Brown precipitate
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Silver mirror
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No observation
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Brick red precipitate
Question 9
Question
Why is a silver mirror formed?
Answer
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Al ions oxidised to Al metal
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Silver ions reduced to silver metal
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Silver ions oxidised to silver metal
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Al ions reduced to Al metal
Question 10
Question
What is the equation for the silver mirror being formed?
Answer
-
Ag-(aq) + e+ ---> Ag(s)
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Ag+(aq) ---> Ag(s) + e-
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Ag+(s) + e- ---> Ag(aq)
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Ag+(aq) + e- ---> Ag(s)
Question 11
Question
What observation do you see when Tollen's added to ketone?
Answer
-
No observation
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Silver mirror
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Deep blue solution
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Orange to green colour change
Question 12
Question
What's the reason for no observation?
Answer
-
The reaction is too slow
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Ketones are not reduced by Tollens' reagent
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Ketones are not oxidised by Tollens' reagent
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Ketones are just dead
Question 13
Question
What's the oxidising species in Tollens' reagent?
Answer
-
Ag(aq)
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Br+(aq)
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Ag(s)
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Ag+(aq)
Question 14
Question
What conditions are required for these reactions?
Answer
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Warm
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Reflux
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conc H2SO4
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Alkaline
Question 15
Question
Filter and [blank_start]recrystallise[blank_end] product. Measure [blank_start]melting point[blank_end] of purified product which is very [blank_start]high[blank_end]. Compare the melting point to a [blank_start]database[blank_end] or [blank_start]data table[blank_end] to identify the unknown product and therefore the [blank_start]original[blank_end] carbonyl compound.
Answer
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recrystallise
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melting point
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high
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database
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data table
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original
Question 16
Question
Why does the yellow/orange solid have to be recrystallised?
Answer
-
Because it needs to be crystallised again
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Because its slightly impure
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Because it's fun
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Because it needs to be more solid
Question 17
Question
Why can't boiling points be used to distinguish between aldehydes and ketones?
Answer
-
It's not possible to know all of the boiling points for every single one
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It will all boil away
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Some are very close together/similar
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It's not accurate enough
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