Tests for gases and (ions )

Question 1

What is the test to identify hydrogen (H2)?

What shows a positive result?

Answer 1

1) add magnesium ribbon to the test tube
2) add 2cm of HCl and quickly cover he top with another test tube
3) put a lit splint into the test tube

squeaky pop

Question 2

What is the test to identify oxygen (O2)?

What shows a positive result?

Answer 2

1) add 1/2 spatula of magnese(IV) oxide to test tube
2) add 2cm of hydrogen peroxide and quickly cover the top with another test tube
3) light a splint, blow it out and put it in the top of the test tube

splint relights

Question 3

What is the test to identify carbon dioxide (CO2)?

What shows a positive result?

Answer 3

1) in a boiling tube add some marble chips
2) put 2cm of lime water into test tube
3) put end of delivery tube into lime water
4) quickly add 2cm of HCl to the boiling tube and quickly add the bung

limewater turns cloudy

Question 3

What is the test to identify ammonia (NH3)?

What shows a positive result?

Answer 3

damp red litmus paper

turns blue

Question 4

What is the test to identify chlorine (Cl2)?

What shows a positive result?

Answer 4

damp blue litmus paper

turns red then bleaches

Question 5

What is the test for positive ions with sodium hydroxide solution?

Answer 5

1) add sodium hydroxide solution drop by drop to each test tube containing the test solution
2) swirl after each drop and observe for any precipitate formed (record the colour)
3) if no precipitate forms, test for ammonia with red litmus paper

Question 6

What is the test for negative ions - testing for carbonates (CO3 2-)?

What type of reaction is this?

Answer 6

1) carefully add dilute HCl to the substance
(carbonates fizz because they give off carbon dioxide)
2) carry out limewater test (bubble CO2 through a small amount of lime water, if it turns cloudy then CO2 is present)

neutralisation reaction

Question 7

What is the test for negative ions - testing for sulphate (SO4 2-)?

What shows a positive test?

What type of reaction is this?

Answer 7

1) dissolve sulphate in still water
2) add dilute HCl
3) put 2cm of this solution into other test tube
4) add barium chloride solution drop by drop

dense white precipitate

precipitaion reaction

Question 8

What is the test for negative ions - testing for halide (chloride, bromide, iodide)?

What colour precipitate is formed with each halide?

What type of reaction is this?

Answer 8

1) dissolve halide in distilled water
2) add 2cm of halide solution in a test tube
3) add a few drops of dilute HNO3
4) add 6-12 drops of silver nitrate solution

chloride (Cl-) - white
bromide (Br-) - cream
iodide (I-) - yellow

precipitation reaction