RP6- Organic Analysis

Question 1

How would you identify an alkene?

Answer 1

add bromine water, would turn orange to colourless

Question 2

Give a test that can be used to identify an aldehyde?

Answer 2

• use Tollen’s reagent, and warm gently
• if an aldehyde is present, silver mirror will form

Question 3

Give a test to identify the presence of primary and secondary alcohols

Answer 3

• add acidified Potassium dichromate
• turns from orange to green if present

Question 4

Why will tertiary alcohols not turn orange in the presence of Potassium dichromate?

Answer 4

As it is not able to be oxidised

Question 5

What does Fehling’s reagent test for? How is it carried out?

Answer 5

• the presence of aldehydes
• add Fehling’s reagent and warm gently
• if present, solution will turn from blue to brick red

Question 6

What is a test for a carboxylic acid?

Answer 6

• add sodium carbonate
• CO2 is produced
• gas is collected and tested with limewater
• will turn cloudy if CO2

Question 7

How is the test for an aldehyde carried out using Tollens’ reagent?

Answer 7

• Mix aqueous silver nitrate with aqueous sodium hydroxide.
• add concentrated ammonia solution until ppt. dissolves
• add few drops of solution, heat
• silver mirror will form

Question 8

How is IR spectroscopy used to identify compounds with the same functional groups?

Answer 8

• compare fingerprint regions with data fromknown spectra

Question 9

What tests for any type of alcohol? include the expected positive result?

Answer 9

warm with ethanoic acid and conc H2SO4
add Na2CO3 to neutralise
sweet smell of an ester

Question 10

Describe the test for a haloalkane? and the possible results?

Answer 10

warm with NaOH
add acidified AgNO3
ppt forms (Cl- white, Br- cream, I- yellow)

Question 11

Write an equation for the oxidation of propan-1-ol to propanoic acid, use [O] to represent the oxidising agent

Answer 11

CH3CH2CH2OH + [O] –> CH3CH2CHO + H2O

Question 12

what colour change is observed when an alcohol is oxidised?

Answer 12

orange (Cr2O7 2-) to green (Cr3+)

Question 13

What safety precautions should be taken when using acidified potassium dichromate?

Answer 13

• gloves as corrosive
• safety goggles
• wash hands after use

Question 14

Why are anti-bumping granules used?

Answer 14

prevents large bubbles forming, which makes the boiling smoother and prevents glass from breaking

Question 15

How can sodium be used to test for an alcohol?

Answer 15

add to a solution
effervescence shows alcohol is present