Chemical analysis

Question 1

Colour of an aqueous, dilute solution of copper(II) ions.

Answer 1

Blue

Question 2

Colour of an aqueous, dilute solution of iron(II) ions.

Answer 2

Green

Question 3

Colour of an aqueous, dilute solution of chromium(III) ions.

Answer 3

Green

Question 4

Colour of an aqueous, dilute solution of iron(III) ions.

Answer 4

Brown / yellow

Question 5

Colour of an aqueous, dilute solution of cobalt(II) ions.

Answer 5

Red / pink

Question 6

Colour of an aqueous, dilute solution of chromate(VI) ions.

Answer 6

Yellow

Question 7

Flame colour of Na⁺

Answer 7

Yellow

Question 8

Flame colour of K⁺

Answer 8

Lilac

Question 9

Flame colour of Ca²⁺

Answer 9

Yellow-red

Question 10

Flame colour of Ba²⁺

Answer 10

Pale green

Question 11

Flame colour of Li⁺

Answer 11

Red

Question 12

Flame colour of Sr²⁺

Answer 12

Red

Question 13

Flame colour of Rb⁺

Answer 13

Red-violet

Question 14

State the observations for the reactions of Cr³⁺(aq) with aqueous sodium
hydroxide.

Answer 14

NaOH(aq):
Green precipitate

Excess NaOH(aq):
Precipitate dissolves to a dark green solution

Question 15

State the observations for the reactions of Fe²⁺(aq) with aqueous sodium
hydroxide.

Answer 15

NaOH(aq):
Green precipitate, turning brown on exposure to air

Excess NaOH(aq):
Precipitate is insoluble

Question 16

State the observations for the reactions of Fe³⁺(aq) with aqueous sodium
hydroxide.

Answer 16

NaOH(aq):
Red-brown precipitate

Excess NaOH(aq):
Precipitate is insoluble

Question 17

State the observations for the reactions of Co²⁺(aq) with aqueous sodium hydroxide.

Answer 17

NaOH(aq):
Blue precipitate, turning pink on standing

Excess NaOH(aq):
Precipitate is insoluble

Question 18

State the observations for the reactions of Cu²⁺(aq) with aqueous sodium
hydroxide.

Answer 18

NaOH(aq):
Blue precipitate

Excess NaOH_(aq):
Precipitate is insoluble

Question 19

State the observations for the reactions of group 2 cations with aqueous sodium hydroxide.

Answer 19

NaOH(aq):
White precipitate

Excess NaOH(aq):
Precipitate is insoluble

Question 20

State the observations for the reactions of group 1 cations with aqueous sodium hydroxide.

Answer 20

No precipitate

Question 21

State the observations for the reactions of Cr³⁺(aq) with aqueous ammonia.

Answer 21

NH₃(aq):
Green precipitate

Excess NH₃(aq):
Precipitate slowly dissolves to a violet solution

Question 22

State the observations for the reactions of Fe²⁺(aq) with aqueous ammonia.

Answer 22

NH₃(aq):
Green precipitate turning brown on exposure to air

Excess NH₃(aq):
Precipitate is insoluble

Question 23

State the observations for the reactions of Fe³⁺(aq) with aqueous ammonia.

Answer 23

NH₃(aq):
Red-brown precipitate

Excess NH₃(aq):
Precipitate is insoluble

Question 24

State the observations for the reactions of Co²⁺(aq) with aqueous ammonia.

Answer 24

NH₃(aq):
Blue precipitate

Excess NH₃(aq):
Precipitate dissolves to a brown solution

Question 25

State the observations for the reactions of Cu²⁺(aq) with aqueous ammonia.

Answer 25

NH₃(aq):
Blue precipitate

Excess NH₃(aq):
Precipitate dissolves to a deep blue solution