Pure Substances

Question 1

How do you test for hydrogen ?

Answer 1

1.) hold a lit splint at the end of a test tube containing hydrogen
2.)you’ll get a squeaky pop
3.) noise come from hydrogen burning rapidly

Question 2

How do you test for oxygen ?

Answer 2

If you put a glowing splint in a test tube ,if it relights,oxygen is present.

Question 3

How can you test for carbon dioxide ?

Answer 3

Blowing bubbles in an aqueous solution of calcium hydroxide(limewater) causes the solution to go cloudy.
This mean co2 was present

Question 4

How do you test for chlorine gas ?

Answer 4

Chlorine bleaches damp litmus paper white if present

Question 5

Test for halide negative ions

Answer 5

1.) add a couple of drops of dilute nitric acid followed by a couple drops of silver nitrate solution to unknown solution
2.) chlorine gives a WHITE precipitate of silver chloride
3.) bromine gives a CREAM precipitate silver bromide
4.) iodine gives a YELLOW precipitate silver iodide

Question 6

Test for metal ions

Answer 6

You can test various metals by heating and seeing whether it burns with distinctive colour

Lithium ions burn with a crimson flame
Sodium ions burn with a yellow flame
Potassium ions burn with a lilac flame
Calcium ions burns with an orange-red flame
Copper ions burn with a green flame

Question 7

How do you test for sulfates?

Answer 7

1.) to identify sulfate ions use a dropping pipette and drop dilute hydrochloride acid followed by barium chloride to a test tube containing mystery solution
2.) if sulfate is present a white precipitate of barium sulfate will form

Question 8

How do you test for carbonates?

Answer 8

1.) to test if a solution has carbonate ions by dropping dilute acid.
2.) connect test tube to another test tube of lime water
3.)if carbonate ions are present, carbon dioxide will be released causing the lime water to go cloudy

Question 9

Explain how metals form a coloured precipitate with sodium hydroxide

Answer 9

Metal hydroxides are insoluble can be used to test metal ions

1.)In the test add a sodium hydroxide to a solution of mystery compound
2.)if you get a coloured insoluble hydroxide you can identify the metal

Calcium 2+—> white precipitate
Copper 2+ —> blue precipitate
Iron 2+—> green precipitate
Iron 3+ —> brown precipitate
Aluminium 3+ —>white precipitate
Magnesium 2+ —> white precipitate

Question 10

Explain what flame emmsion spectroscopy