required practical 4: testing for anions and cations

Question 1

what is the test for a sulfate ion

Answer 1

BaCl2 acidified with HCl
white ppt will form of BaSO4
fizzing observed due to CO2 if a carbonate was present

Question 2

wha is the test for halides

Answer 2

add nitric acid - react with any carbonates to prevent formation of Ag2CO3
add silver nitrate
chlorides produce a white ppt of AgCl
bromides produce a cream ppt of AgBr
iodides produce a yellow ppt of AgI

Question 3

how do you differentiate between silver halides

Answer 3

silver chloride will dissolve in dilute ammonia
silver bromide will dissolve in conc ammonia
silver iodide will not dissolve

Question 4

what is the test for carbonate ions

Answer 4

add dilute acid
bubble the gas through limewater
CO2 will turn the limewater cloudy

Question 5

what is the test for hydroxide ion

Answer 5

add NaOH (sample)
turns damp red litmus paper blue

Question 6

reaction between bromide and sulfuric acid

Answer 6

white steamy fumes -HBr
orange fumes - Br2
colourless gas - SO2

Question 6

reaction between fluoride and chloride with sulfuric acid

Answer 6

white steamy fumes

Question 7

reaction between iodide and sulfuric acid

Answer 7

white steamy fumes - HI
black solid and purple fumes - I2
colourless gas - SO2
yellow solid - S
gas with pungent egg smell - H2S

Question 8

what is the test for ammonium ions

Answer 8

add ammonium chloride to NaOH
heat via warm water bath
damp red litmus paper turns blue

Question 9

what is the reaction of NaOH with group 2

Answer 9

MgCl2 - slight white ppt ( forms white ppt with excess NaOH)
CaCl2 - slight whit ppt
SrCl2 - slight white ppt
BaCl2 - colourless

Question 10

what is the reaction of dilute sulphuric acid with group 2

Answer 10

Ba - white ppt
Mg - slight white ppt (goes colourless in excess sulphuric acid)
Ca - slight white ppt
Sr - white ppt