TESTS

Question 1

test for chlorine?

Answer 1

damp blue litmus paper goes from blue to white (however it may turn red first as Cl + H2O = HCl)

Question 2

precautions for testing for chlorine

Answer 2

since its poisonous wear a mask or do it in a fume cupboard

Question 3

test for oxygen?

Answer 3

it relights a glowing splint. put it in test tube with oxygen

Question 4

test for hydrogen?

Answer 4

lighting splint placed in test tube with hydrogen results in a squeaky pop

Question 5

test for carbon dioxide?

Answer 5

bubble gas sample in limewater (calcium hydroxide) turns lime water milky

Question 6

test for ammonia

Answer 6

turns damp red litmus paper blue

Question 7

test for sulfur dioxide

Answer 7

turns acidified aqueous potassium manganate(VII) from purple to colourless

Question 8

test for carbonate ions

Answer 8

add dilute HCl to test sample then bubble the gas produced into lime water. turns milky, cloudy

Question 9

test for sulfate ions

Answer 9

add dilute HCl to sample then add barium chloride or nitrate to the solution
positive test is white precipitate is formed

Question 10

test for halide ions [chloride, bromide and iodide ions]

Answer 10

add dilute nitric acid to sample to get rid of impurities
then add silver nitrate
silver + halide ion = precipitate
Cl ion = silver chloride (white prec.)
Bromide ion = silver bromide (cream prec.)
Iodide ion = silver iodide (yellow prec.)

Question 11

how to carry out flame tests

Answer 11

Take a platinum wire loop, and clean it by dipping it in some dilute hydrochloric acid, rinsing it in distilled water, and then heating it over a Bunsen burner flame.

Dip the wire loop into the compound you want to test.
Hold the wire loop in the clear blue part of the Bunsen burner flame (this is the hottest part).

See what colour the flame turns as the compound burns.

Question 12

colour of flame tests

Answer 12

lithium - red flame
sodium - yellow flame
potassium - lilac flame
calcium - orange-red flame
barium - light green flame
copper - blue - green flame

Question 13

when there are multiple colours you use metal hydroxide test, specifically sodium hydroxide. what colour do the metal ions turn?

Answer 13

copper - blue precipitate
calcium - white precipitate
iron (II) - green precipitate
iron (III) - brown precipitate
magnesium - white prec.
aluminium - white prec. but in excess NaOH forms colourless sol.

Question 14

test for presence of water

Answer 14

Water turns cobalt chloride paper or anhydrous cobalt (II) chloride from blue to pink. (This is due to formation of hydrated Cobalt (II) Chloride).
CoCl2 (s) + 6H2O (l) = CoCl2.6H2O (s)
blue pink

OR
Water turns anhydrous Copper (II) Sulfate from white to blue. This us due to formation of hydrated copper (II) sulfate.
CuSO4 (s) + 5H2O (l) CuSO4.5H2O (s)
white blue