Chapter 7 2024/2025

a) Dimethylamine, (CH3)2NH is a colourless liquid with an ammonia-like odour. The ionisation constant, Kb for (CH3)2NH is 5.9 x10-4. Determine the pH of 1.5 M of (CH3)2NH solution. 

[5 Marks]

b) A salt is produced when sodium hydroxide solution, NaOH reacts with hydrocyanic acid, HCN. Classify the salt formed according to its acid-base properties.  

[4 Marks]

c) The solubility product of magnesium phosphate, Mg3(PO4)2 is 5.2 x 10-24.  

i. Calculate the molar solubility of Mg3(PO4)2.    

[4 Marks] 

ii. Explain the effect on the molar solubility when magnesium chloride solution is added into the above salt solution.     

[2 Marks]