Tests for anions, cations, functional groups...

Question 1

Test for acid/base character

Answer 1

acid- red

base- blue

Question 2

Flame test for Li+

Answer 2

Red

Question 3

Flame test Na+

Answer 3

orange/yellow

Question 4

Flame test K+

Answer 4

lilac

Question 5

Flame test Rb+

Answer 5

red

Question 6

Flame test Cs+

Answer 6

blue

Question 7

Flame test Mg2+

Answer 7

no color

Question 8

Flame test Ca2+

Answer 8

brick-red

Question 9

Flame test Sr2+

Answer 9

crimson red

Question 10

Flame test Ba2+

Answer 10

green

Question 11

Test for CO32- and HCO3-

Answer 11

add acid(aq)
bubbles of co2 observed
use delivery tube to pass gas through limewater
limewater turns cloudy, CaCO3 formed

Question 12

Test for NH4+ ions

Answer 12

add NaOH(aq) and warm gently
pungent smell given off
turns damp red litmus paper blue

Question 13

Test for SO42-

Answer 13

Add BaCl2

white ppt of BaSO4 formed

Question 14

Test for Halides

Answer 14

HNO3 followed by AgNO3
Cl-:white ppt soluble in ammonia
Br-: cream ppt soluble in excess ammonia
I-: yellow ppt insoluble in ammonia

Question 15

Test for Mg2+

Answer 15

Add NaOH: white suspension

Add more NaOH: insoluble

Question 16

Test for Ca2+

Answer 16

Add NaOH: white suspension

Add more NaOH: partially in soluble

Question 17

Test for Sr2+ and Ba2+

Answer 17

Add NaOH: soluble

Add more NaOH: soluble

Question 18

Test for Zn2+

Answer 18

Add NaOH: white ppt soluble in NH3
Add more NaOH:ppt dissolves
Zn is amphoteric

Question 19

Test for Al3+

Answer 19

Add NaOH: white ppt
Add more NaOH: ppt dissolves
Al is amphoteric

Question 20

Test for Ag+

Answer 20

Add NaOH: dark brown ppt soluble in NH3

Add more NaOH: insoluble

Question 21

Test for Cu2+

Answer 21

Add NaOH: blue ppt soluble in excess ammonia blue solution

Add more NaOH: insoluble

Question 22

Test for Fe2+

Answer 22

Add NaOH: white/green ppt slowly turns brown when exposed to air
Add more NaOH: insoluble

Question 23

Test for Fe3+

Answer 23

Add NaOH: brown ppt

Add more NaOH: insoluble

Question 24

Test for Cr3+

Answer 24

Add NaOH: blue-green ppt soluble in NH3 to give violet solution
Add more NaOH:ppt dissolves to give green solution

Question 25

Test for Co2+

Answer 25

Add NaOH: blueish ppt slowly turns pink, dissolves in NH3 light brown solution Add more NaOH:insoluble

Question 26

Test for Ni2+

Answer 26

Add NaOH: green ppt soluble in NH3 to give blue solution | Add more NaOH: ppt doesn't dissolve

Question 27

Test for Mn2+

Answer 27

Add NaOH: off-white ppt turns brown in exposure to air | Add more NaOH:insoluble

Question 28

Test for halides with conc H2SO4

Answer 28

Cl-: steamy fumes of HCl Br-: steamy fumes, brown vapour I-: steamy fumes, purple vapour, black solid

Question 29

Test for bromides

Answer 29

add chlorine water orange solution Effervescence may be produced

Question 30

Test for alkenes

Answer 30

add some bromine water | color change from orange to colourless

Question 31

Test for -OH groups (not phenols)

Answer 31

``` add PCl5 misty fumes of HCl or add a small piece of sodium effervescence ```

Question 32

Test for carboxylic acids

Answer 32

litmus paper turns red-ish. Add a carbonate/HCO3​ −​ Effervescence (CO2​ )​

Question 33

Test for aldehydes and ketones

Answer 33

Add 2,4-DNP (Brady’s reagent). | An orange precipitate is formed upon reaction with C=O group of aldehyde or ketone.

Question 34

Test to distinguish aldehydes from ketones

Answer 34

Add Tollen’s Solution(ammoniacal AgNO3​)​. Aldehydes give a positive test and a silver mirror is observed. Ketones cannot be oxidised, so no change observed) or Fehling’s test. Aldehydes give a positive test and form a brick red precipitate. Ketones don’t react so the solution stays deep blue).

Question 35

Test for methylketones, ethanal, ethanol, and methyl secondary alcohols

Answer 35

Iodoform Reaction Warm with iodine and sodium hydroxide. Yellow precipitate. Antiseptic smell (triiodomethane, iodoform).

Question 36

Test for primary/secondary alcohol and aldehydes

Answer 36

warm with acididfied K2Cr2O7 | color change from orange to green

Question 37

Esterification test

Answer 37

Gently warm an alcohol and carboxylic acid in presence of conc. H2​ S​ O4​ Should produce a compound with a characteristic smell

Question 38

Solubility Test

Answer 38

Compounds with groups that can form H-bonds may be soluble in water, (e.g. amines, alcohols, carboxylic acids etc.) Some carboxylic acids may not be soluble in water, but may be soluble in alkaline solution (due to formation of RCOO−​ )​ . Same goes with amines. Some may not be soluble in water, but will be soluble in acidic solution (e.g. formation of RNH3​ +​ )​