Analysis

Question 1

what are the two tests for positive ions?

Answer 1

flame test
adding aqueous sodium hydroxide

Question 2

results of flame test?

Answer 2

Li+ Bright red
Na+ Golden yellow
K+ Lilac
Cu2+ Green/blue
Ca2+ Brick red
Al3+ N/A
Fe2+ N/A
Fe3+ N/A
NH4 + N/A
Ba2+ apple green

Question 3

results of adding aqueous sodium hydroxide?

Answer 3

Li+ NVR
Na+ NVR
K+ NVR
Cu2+ blue ppt
Ca2+ white ppt (unchanged with excess NaOH)
Al3+ white ppt (redissolves with excess NaOH)
Fe2+ green ppt
Fe3+ brown ppt
NH4 + NVR, but if heated, ammonia produced
Ba2+ white ppt

Question 4

what are the three tests for negative ions

Answer 4

• add dilute acid
• add BaCl2 and HCl
• add AgNO3 and HNO3

Question 5

results of adding dilute acid?

Answer 5

CO3 2- : fizzing, carbonate ‘dissolves’
SO4 2- : NVR
Cl - : NVR
Br - : NVR
I - : NVR

Question 6

results of adding BaCl2 and HCl

Answer 6

CO3 2- : white ppt forms, redissolves when HCl added
SO4 2- : white ppt forms, stays with HCl
Cl - : NVR
Br - : NVR
I - : NVR

Question 7

results of adding AgNO3 and HNO3

Answer 7

CO3 2- : NVR
SO4 2- : NVR
Cl - : white ppt forms
Br - : cream ppt forms
I - : yellow ppt forms

Question 8

why are instrumental methods of analysis better?

Answer 8

• very sensitive
• very fast
• very accurate

Question 9

what is flame photometry?

Answer 9

substance put into flame
light emitted
flame photometer records wavelengths of light emitted
can then identify positive ions
can identify multiple positive ions in a mixture

Question 10

test for water?

Answer 10

• anhydrous copper sulfate goes from white to blue
• cobalt chloride paper goes from blue to pink

Question 11

test for ammonia gas?

Answer 11

damp red litmus paper turs blue

Question 12

test for carbon dioxide?

Answer 12

bubble through limewater, goes cloudy if present

Question 13

test for hydrogen?

Answer 13

hold lit splint under collection of gas, squeaky pop sound signifies presence

Question 14

test for oxygen?

Answer 14

glowing splint is relit

Question 15

test for alkenes?

Answer 15

mix it with bromine water, brown bromine water turns colourless

Question 16

test for chlorine?

Answer 16

damp blue litmus paper turns red, then is bleached white