Cation Tests

Question 1

what type of ions are cations?

Answer 1

positive ions e.g. Na+

Question 2

how do you conduct a flame test?

Answer 2

1. dip a piece of nichrome/platinum wire into hydrochloric acid - these wires don’t colour the flame, and the acid cleans the wire
2. dip the wire into a sample of solid or solution - this causes some of the sample to stick onto the wire
3. place the tip of the wire into a non-luminous Bunsen flame

Question 3

what colour flame does Li+ have?

Answer 3

red

Question 4

what colour flame does Na+ have?

Answer 4

yellow

Question 5

what colour flame does K+ have?

Answer 5

lilac

Question 6

what colour flame does Ca2+ have?

Answer 6

orange-red

Question 7

what colour flame does Cu2+ have?

Answer 7

blue-green

Question 8

what do we use to test for ammonium ions?

Answer 8

sodium hydroxide

Question 9

how to conduct an ammonium test?

Answer 9

1. dissolve the sample in water
2. add some NaOH (aq) and warm it
3. test the gas evolved with damp red litmus paper

Question 10

if ammonium ions are present in the test sample, what colour will the litmus paper turn?

Answer 10

blue