C4.2.2 - Detecting cations

Question 1

What is the flame test?

Answer 1

A test that helps identify metal ions in compounds from the colour they produce in a flame

Question 2

What coloured flame does lithium produce?

Answer 2

Red

Question 3

What coloured flame does sodium produce?

Answer 3

Yellow

Question 4

What coloured flame does potassium produce?

Answer 4

Lilac

Question 5

What coloured flame does calcium produce?

Answer 5

Orange-red

Question 6

What coloured flame does copper produce?

Answer 6

Green-blue

Question 7

What are hydroxide precipitate tests?

Answer 7

Adding a few drops of sodium hydroxide to a solution containing metal ions, and note the colour of an precipitate formed?

Question 8

What is the colour of an iron(II) hydroxide precipitate?

Answer 8

Green

Question 9

What is the colour of an iron(III) hydroxide precipitate?

Answer 9

Orange-brown

Question 10

What is the colour of a copper(II) hydroxide precipitate?

Answer 10

Blue

Question 11

What is the colour of a calcium hydroxide precipitate

Answer 11

White

Question 12

What is the colour of a zinc hydroxide precipitate?

Answer 12

White

Question 13

What happens to zinc hydroxide if you add an excess of sodium hydroxide solution?

Answer 13

It dissolves to form a colourless solution

Question 14

What happens to calcium hydroxide if you add an excess if sodium hydroxide solution?

Answer 14

It does not dissolve

Question 15

What equipment is needed for a flame test?

Answer 15

• A Bunsen burner
• a nichrome wire loop
• hydrochloride acid to clean the loop several times
• distilled water to help clean the loop as well

Question 16

How do you test a substance in a flame test?

Answer 16

1. Dip the clean loop into the test powder of a solution
2. Use the handle to hold the loop in the edge of a roaring blue flame
3. Record the flame colour
4. Clean the wire loop after to avoid contamination with previous test substances and repeat again with other substances