RP 11: Exam Questions

Question 1

When anhydrous aluminium chloride reacts with water, solution Y is formed that
contains a complex aluminium ion, Z, and chloride ions.

Describe two observations you would make when an excess of sodium carbonate
solution is added to solution Y.
Give an equation for the reaction. In your equation, include the formula of each
complex aluminium species.

Answer 1

white ppt/solid
effervescence/bubbles/fizzing
2[Al(H2O)6]
3+ + 3CO3
2–  2[Al(H2O)3
(OH)3] + 3CO2 + 3H2O

Question 2

When anhydrous aluminium chloride reacts with water, solution Y is formed that
contains a complex aluminium ion, Z, and chloride ions.

Aqueous potassium hydroxide is added, until in excess, to solution Y.
Describe two observations you would make.
For each observation give an equation for the reaction that occurs.
In your equations, include the formula of each complex aluminium species

Answer 2

White ppt/solid
[Al(H2O)6]
3+ +3OH– -> [Al(H2O)3(OH)3] + 3H2O

Colourless solution forms / ppt or solid dissolves

[Al(H2O)3(OH)3] + OH -> [Al(H2O)2(OH)4]
–
+ H2O