Topic 9a- Chemical analysis / tests for ions

Question 1

Flame test: Lithium

Answer 1

Red

Question 2

Flame test: Sodium

Answer 2

Orange/Yellow

Question 3

Flame test: Potassium

Answer 3

Lilac

Question 4

Flame test: Calcium

Answer 4

Brick red/orange

Question 5

Flame test: Barium(?)

(not on spec)

Answer 5

apple green

Question 6

Why is only a small amount of NaOH is used?

Answer 6

So the metal hydroxide precipitates
In excess NaOH some of the precipitates may dissolve

Question 6

Flame test: Copper

Answer 6

green/blue

Question 6

What is used to test for cations?

Answer 6

NaOH (sodium hydroxide)

Question 6

Sodium hydroxide test: copper

Answer 6

Light blue precipitate, remains in excess (insoluble)

Question 6

Sodium hydroxide test: Ammonium ions (NH4 (+))

Answer 6

No precipitate, gentle heating produces ammonia gas that can be tested for with red litmus paper, turning blue

Question 7

Sodium hydroxide test: Calcium

Answer 7

White precipitate, remain in excess (insoluble)

Question 7

Sodium hydroxide test: Aluminium

Answer 7

White precipitate, dissolve in excess

Question 7

Sodium hydroxide test: Iron(II)

Answer 7

Green precipitate, remains in excess (insoluble)

Question 8

Sodium hydroxide test: Iron(III)

Answer 8

Red-brown precipitate, remains in excess (insoluble)

Question 9

Test for carbonate ions

Answer 9

Add dilute acid, effervescance seen, CO2 produced, lime water test

Question 10

test for sulfate ion

Answer 10

Add dilute HCl and aqueous barium chloride, white precipitate of barium sulfate formed

Question 11

How to test for halide ions?

Answer 11

Add dilute nitric acid (HNO3) then add silver nitrate solution (AgNO3), forms silver halide precipitate forms

Question 12

What colour is silver chloride?

Answer 12

White

Question 13

What colour is silver bromide?

Answer 13

Cream

Question 14

What colour is silver iodide?

Answer 14

Yellow