ion tests

Question 1

flame test for calcium

Answer 1

brick red

Question 2

flame test for strontium

Answer 2

red

Question 3

flame test for barium

Answer 3

pale green

Question 4

test tube test for magnesium

Answer 4

+OH - = slight white precipitate
excess OH- = white precipitate

Question 5

test tube test for calcium

Answer 5

+OH - = slight white precipitate
excess OH- = slight white precipitate

Question 6

test tube test for strontium

Answer 6

+OH - = slight white precipitate
excess OH- = slight white precipitate

Question 7

test for ammonium ion

Answer 7

• add OH- ions (sodium hydroxide)
• gently heat
• test gas evolved with damp red litmus paper, will turn blue if present

NH4+ + OH- = NH3 + H2O

Question 8

test tube test for barium

Answer 8

+OH - = no change
excess OH- = no change

Question 9

sulfate test

Answer 9

• add dilute HCl
• add barium chloride solution (BaCl2)

Ba 2+ + SO4 2- = BaSO4 (s)

white precipitate is formed

HCl is added to remove any carbonate ions which would interfere

Question 10

test for hydroxides

Answer 10

• dip red litmus paper into solution
• if OH- ions are present, the paper will turn blue

Question 11

test for halides

Answer 11

• add dilute nitric acid
• add silver nitrate solution

Chloride - white ppt (soluble in conc and dilute ammonia)

Bromide - cream ppt (only soluble in conc ammonia, not dilute)

Iodide - yellow ppt (insoluble in both conc and dilute ammonia)