Precipitates of Complex Ions

Question 1

What is the colour change observed when Cu2+ ( copper (II) ) reacts with hydroxide?

Answer 1

Blue solution –> blue precipitate

Question 2

What is the colour change observed when Fe2+ ( iron (II) ) reacts with hydroxide?

Answer 2

Pale green solution –> green precipitate

Question 3

What is the colour change observed when Fe(OH)2 is exposed to air and why does this change occur?

Answer 3

Green precipitate –> Orange-brown precipitate

Fe2+ is oxidised to Fe3+.

Question 4

What is the colour change observed when Fe3+ ( iron (III) ) reacts with hydroxide?

Answer 4

Pale yellow solution –> orange-brown precipitate

Question 5

What is the colour change observed when Mn2+ ( manganese (II) ) reacts with hydroxide?

Answer 5

Pale pink solution –> light brown precipitate

Question 6

What is the colour change observed when Mn(OH)2 is exposed to air?

Answer 6

Light brown precipitate darkens

Question 7

What is the colour change observed when Cr3+ ( chromium (III) ) reacts with hydroxide?

Answer 7

Violet solution –> grey-green precipitate

Question 8

What is the colour change observed when Cr(OH)3 dissolves in excess NaOH?

Answer 8

Grey-green precipitate –> dark green solution

Question 9

What is the formula of the dark green solution formed when Cr(OH)3 dissolves in excess NaOH?

Answer 9

[Cr(OH)6]3-

Question 10

What is the colour changed observed when Cu2+(aq) reacts with Cl-

Answer 10

Pale blue solution —-> yellow solution

Question 11

What is the colour changed observed when Cu2+ (aq) reacts with NH3

Answer 11

Pale blue solution to dark blue solution

Question 12

What is the colour changed observed when Cr3+ (aq) reacts with NH3 dropwise

Answer 12

Violet solution –> grey green precipitate

Question 13

What is the colour change observed when Cr3+(aq) reacts with excess ammonia(aq)

Answer 13

Violet solution to purple solution