I- Aqua ions =)

Question 1

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Suggest a reagent for the following reaction:
[Fe(H2O)6]3+ –> [Fe(H2O)6]2+
(1)

Answer 1

Zn in acid

Question 2

Write the simplest ionic equation for the reaction that occurs between the green ppt (FeCO3) and sulfrusic acid. (1)

Answer 2

2H+ + CO3 2- –> H2O + CO2

Question 3

Give an equation to show how the complex ion [Al(H2O)6]3+ can act as a Bronsted-Lowry acid with water. (1)

Answer 3

[Al(H2O)6]3+ + H2O(l) –> [Al(H2O)5(OH)]2+ + H3O+ (aq)

Question 4

State the meaning of the term complex ion. (1)

Answer 4

central metal ion surrounded by co-ordinately-bonded ligands

Question 4

State the meaning of the term ligand. (1)

Answer 4

• an atom, ion, or molecule
• which can donate a lone e- pair

Question 5

State the meaning of the term co-ordination number. (1)

Answer 5

no. of co-ordinate bonds formed to central metal ion

Question 6

An aqueous solution of iron (II) sulphate is a pale-green colour.
Give thr formula of the complex ion responsible for the pale-green colour. (1)

Answer 6

[Fe(H2O)6]2+

Question 7

An aqueous solution of iron (II) sulphate is a pale-green colour.
When aqueous sodium hydroxide is added to this solution, a green precipitate is formed.
Give the formula of the green precipitate. (1)

Answer 7

[Fe(OH)2(H2O)4]

Question 8

In a solution containing a green precipitate of [Fe(OH)2(H2O)4] slowly turned brown on standing in air.
Suggest an explanation for the change in colour of the precipitate. (2)

Answer 8

• Fe2+ oxidised into Fe3+
• by O2 in air

Question 9

State what is observed when an excess of aqueous ammonia reacts with an aqueous iron (II) salt.
Write an equation for this reaction. (4)

Answer 9

[Fe(H2O)6]2+ +2NH3 –> [Fe(OH)2(H2O)4] + 2NH4 +
- pale green solution
- green ppt formed
- insoluble in XS NH3

Question 10

A solution absorbs light with wavelengths corresponding to red, yellow and green light.
Which ion is most likely to be in the solution?
A. Cr2O7 2-
B. Fe2+
C. Fe3+
D. Cu2+
(1)

Answer 10

D!
- absorbs red, yellow green; transmits blue light only

Question 11

Which compound gives a colourless solution when an excess of dilute ammonia is added?
A. MgCl2
B. AgCl
C. CuCl2
D. AlCl3

Answer 11

B

Question 12

Deduce the role of copper metal in the formation of [CuCl4]3- from [CuCl4]2- . (1)

Answer 12

reducing agent

Question 13

Name the shape of the [CuCl4]2– ion. (1)

Answer 13

tetrahedral

only 4 Cl fit around Cu!!!!