test for cations and anions

Question 1

test for metal ions (cations)

Answer 1

1. clean wire loop with hydrochloric acid
   2.dip the wire loop in the compound
2. place it over the clear blue flame
3. the colour it produces will tell u what metal ion is present

Question 2

what colour flame will be produced for each metal ion present

Answer 2

lithium Li+ red flame
calcium ca2+ orange-red flame
sodium Na+ yellow flame
potassium K+ lilac flame
copper cu2+ green flame

Question 3

the other test for metal ions using sodium hydroxide

Answer 3

1. add sodium hydroxide solution to the insoluble metal hydroxide

2.if precipitate use the colour to see what metal ion is present

Question 4

for the sodium hydroxide metal ion test
name each colour of precipitate for each metal ion present

Answer 4

copper (II) blue
calcium white
iron (II) green
iron (III) brown
magnesium white
aluminium white, colour less when excess sodium hydroxide

Question 5

ionic equation of ca2+ + 2OH-

Answer 5

ca(OH)2

Question 6

test of carbonate ions

Answer 6

1.add hydrochloric acid to the solution
2. if carbonate ions are present carbon dioxide gas will appear
3. collect the gas and run it through limewater
4. if the limewater goes cloudy it confirms that the substance contaminated carbonate ions

Question 7

test for sulfate ions

Answer 7

1. add HCl to the substance
2. add barium chloride solution
   3if sulfate ions are present white precipitate forms

Question 8

in the test for sulfate ions why do we add HCl

Answer 8

to remove any carbonate ions which will give us a white precipitate also

Question 9

test for halide ions

Answer 9

1. react solution with nitric acid
   2.add silver nitrate solution
2. the colour precipitate forms tell u which ion is present

Question 10

in the test for halide ions what colour precipitate tells u which ion is present

Answer 10

chloride white
bromine cream
iodine yellow

Question 11

in the test for halide ions why do we use nitric acid instead of hydrochloric acid

Answer 11

to remove any carbonate or sulfate ions present

Question 12

why is the flame test a bit shit

Answer 12

because it doesnt tell us concentration of the metal ions present

can be wrong due to interpretation of colours

can tell if multiple metal ions are present

Question 13

what could u use instead of the flame test

Answer 13

flame photometry

Question 14

test for ammonium ions

Answer 14

add sodium hydroxide to substance and heat it
if ammonia gas given off ammonia ions are prsesent

Question 15

confirmatory test for ammonium ions

Answer 15

hold piece of damp red litmus paper over it and it will turn blue
ammonia also has strong smell

Question 16

why do we make the litmus paper damp in the test for ammonium ions

Answer 16

because the water acts as a barrier because ammonium gas is irritant and toxic