organic analysis

Question 1

test for alkenes

Answer 1

shake with bromine water
bromine turns from orange to colourless if alkene is present

Question 2

test for primary and secondary alcohols

Answer 2

add acidified K2Cr2O7 and warm
solution turns from orange to green
also for aldehyde

Question 3

test for aldehyde

Answer 3

warm with fehlings solution - blue solution turns brick red
warm with tollens solution - silver mirror forms

Question 4

test for carboxylic acids

Answer 4

add Na2CO3 - carbonates
effervescence will show - CO2 given off

Question 5

test for H2

Answer 5

lit splint - squeaky pop

Question 6

test for CO2 gas

Answer 6

bubble through lime water - solution turns cloudy

Question 7

test for O2 gas

Answer 7

apply a glowing splint - split will relight

Question 8

test for SO42- ions

Answer 8

add BaCl2 solution - a white ppt will form

Question 9

test for halide ions

Answer 9

add HNO3 then AgNO3
white ppt - Cl- ions which will dissolve in dilute ammonia
Cream ppt - Br- ions which will dissolve in conc ammonia
Yellow ppt - I- ions which will remain as insoluble

Question 10

test for CO32- ions

Answer 10

add any acid - effervescence

Question 11

global warming

Answer 11

-when IR hits CO2/H2O/CH4
-O-H bonds in water , C=O bonds CO2 , C-H bonds in CH4 absorb IR radiation
-IR emitted by the earth is not allowed to escape into the atmosphere

Question 12

infrared spectroscopy

Answer 12

infrared energy is absorbed by bonds which makes the bonds vibrate
bonds vibrate at the same frequency as the infrared energy
helps identify the functional group

Question 13

model answer

Answer 13

the spectrum represent a …. because it has a absorption matching the … bond from ….

Question 14

O-H bonds

Answer 14

O-H bond in alcohol - broad and smooth
O-H bond in carboxylic acid - sharp and jagged and more broad

Question 15

fingerprint region

Answer 15

the fingerprint region - area below spectrum 1500cm-1 and below
can’t be interpreted

Question 16

molecular ion peak facts

Answer 16

-peak with the largest m/z values called the ‘molecular ion’ peak
-the m/z ratio of the molecular ion peaks equal to the mr of the molecules

Question 17

high resolution mass spectrometry

Answer 17

low resolution mass spectrometry data is measured to 1dp and 2 molecules can have the same data
high resolution measure to 5dp so they can be differentiated more easily