Precipitation reactions

Question 1

Definition of precipitation

Answer 1

Reaction of two aqueous solution to form an insoluble ionic solid

Question 2

Equation of copper(II) and NaOH

Answer 2

Cu2+(aq) + 2OH-(aq) —> Cu(OH)2(s)

Question 3

Observation of copper(II) and NaOH

Answer 3

Blue solution —> Blue precip.

Question 4

Equation of iron(II) and NaOH

Answer 4

Fe2+(aq) + 2OH-(aq) —> Fe(OH)2(s)
in air: Fe(OH)2(s) —> Fe(OH)3(s)

Question 5

Observation of iron(II) and NaOH

Answer 5

Pale green solution —> Green precip. —> Orange-brown precip.

Question 6

Equation of iron(III) and NaOH

Answer 6

Fe3+(aq) + 3OH-(aq) —> Fe(OH)3(s)

Question 7

Observation of iron(III) and NaOH

Answer 7

Pale yellow solution —> Orange-brown precip.

Question 8

Equation of Mn(II) and NaOH

Answer 8

Mn3+(aq) + 2OH-(aq) —> Mn(OH)2(s)

Question 9

Observation of Mn(II) and NaOH

Answer 9

Pale pink solution —> Light brown precip. that darkens on standing in air

Question 10

Equation of Cr(III) and NaOH

Answer 10

Cr3+(aq) + 3OH-(aq) —> Cr(OH)3(s)
Cr(OH)3(s) + 3OH-(aq) —> [Cr(OH)6]3-(aq)

Question 11

Observation of Cr(III) and NaOH

Answer 11

Violet solution —> Grey-green precip. Cr(OH)3 —> Green solution