C4.2.2 - Detecting Cations

Question 1

What happens when metal ions are heated?

Answer 1

They move into higher electron shells and when they move back to normal energy is transferred to the surroundings as radiation.

Question 2

What are the different colours for different metal ions in the flame test?

Answer 2

Lithium - Red
Sodium - Yellow
Potassium - Lilac
Calcium - Orange Red
Copper - Green Blue

Question 3

Why do you use sodium hydroxide solution over other metal hydroxides in experiments?

Answer 3

Group 1 metal hydroxides are soluble in water but most other metal hydroxides are not

Question 4

What are hydroxide precipitate tests?

Answer 4

Different metals produce different coloured precipitates so you add a few drops of sodium hydroxide solution to a solution containing metal ions taking note of the colour.

Question 5

Name the colour of hydroxide predicates for different ions

Answer 5

Iron(II) - Green
Iron(III) - Orange brown
Copper(II) - Blue
Calcium - White
Zinc - White

Question 6

What happens to calcium hydroxide and zinc hydroxide if you add sodium hydroxide solution

Answer 6

Zinc hydroxide dissolve to form a colourless solution

Calcium hydroxide does not dissolve