GCSE C4.2

Test for carbon dioxide

Test for carbon dioxide

bubble through limewater if present

Test for hydrogen

-hold a lighted splint at the open end of a test tube of gas

• creates a squeaky pop sound

Test for oxygen

place a glowing splint inside a test tube of gas

Test for chlorine

damp blue litmus paper will be bleached white

Colour of Li+ flame test

Red

Colour of Na+ flame test

Yellow

Colour of K+ flame test

Lilac

Colour of Ca 2+ flame test

orange-red

Colour of Cu 2+ flame test

blue-green

Metal ions produce a ...

colour if heated strongly in a flame

How do you carry out a flame test?

• dip the loop of an unreactive metal in dilute acid

How can metal cations in aq solutions be identified?

by the colour of the precipitate they form on addition of sodium hydroxide

What forms a white precipitate with the addition of sodium hydroxide?

Calcium

What forms a blue precipitate with the addition of sodium hydroxide?

Copper (II)

What forms a green precipitate with the addition of sodium hydroxide?

Iron (II)

Orange-brown precipitate with the addition of sodium hydroxide?

Iron (III)

What do all carbonates contain?

the carbonate ion CO3 2-

What is released when carbonates react with dilute acids

carbon dioxide

How to test for carbonate ions?

• add dilute acid then test the gas released

• if a carbonate compound is present then fizzing should be seen and the gas produced is carbon dioxide which turns limewater cloudy when bubbled through

How to test for a sulfate ion?

• acidify the sample with dilute hydrochloric acid

How to test for Halide ions?

• add dilute nitric acid

Instrumental analysis

Faster More accurate Sensitive

The last peak of a mass spectrum tells us...

the relative formula mass of the compound