TESTING FOR CATIONS

Question 1

What do you observe when you add dilute sodium hydroxide to to iron (II) ions?

Answer 1

You observe the formation of a dirty green solid.

Question 2

What do you observe when you add dilute sodium hydroxide to iron (III) ions? (Fe3+)

Answer 2

The formation of an orange/brown precipitate (rust)

Question 3

What do you observe when you add dilute sodium hydroxide to ammonium ions? (NH4+)

Answer 3

A pungent smell and it turns damp red litmus paper blue.

Question 4

What do you observe when you add dilute sodium hydroxide to copper (II) ions? (Cu2+)

Answer 4

The formation of a pale blue solid

Question 5

How do you carry out a flame test?

Answer 5

Use a nichrome wire with a loop at the end, which has been cleaned with dilute HCL. Then hold it over a Bunsen burner.

Question 6

What colour is the flame that lithium burns with? (Li+)

Answer 6

A red flame

Question 7

What colour is the flame that sodium burns with? (Na+)

Answer 7

A yellow orange flame

Question 8

What metal ion burns with a lilac flame?

Answer 8

Potassium (K+)

Question 9

What metal ion burns with a brick red flame?

Answer 9

Calcium (Ca2+)

Question 10

What two ways can be used to test for cations?

Answer 10

Either do the flame test, or use NaOH(aq)