(a)  The ionisation constant, Ka of benzoic acid, C6H5COOH is 6.5x10-5. Determine the pH of 0.186 M of C6H5COOH. 

(b)  A student is asked to prepare a buffer solution at pH 4.6 using 50.00 mL of 0.5 M benzoic acid, C6H5COOH and sodium benzoate, C6H5COONa. Calculate the mass of sodium benzoate required to prepare the buffer solution. Explain the buffering effect of adding a small amount of NaOH into the buffer solution. 

(c) Calculate the solubility of magnesium phosphate, Mg3(PO4)2, in  gL-1.

             [Ksp Mg3(PO4)2 = 5.2 x 10-24, RMM for Mg3(PO4)2 = 262]

(a)  A buffer solution was made by dissolving a mixture of sodium acetate, CH3COONa and acetic acid, CH3COOH in water. Explain how the buffer maintains the pH of a solution when a small amount of strong acid or strong base is added to the buffered solution. An amount of 0.984 g of CH3COONa was dissolved in 100mL of 0.1 M CH3COOH to make an acidic buffer. Calculate the pH of the buffer and state all assumptions made. [Ka CH3COOH = 1.8 x 10-5  ]   

(b)  Lactic acid, HL, is a monoprotic acid. An aqueous solution of 0.1 M lactic acid has a pH of 2.43. Calculate the Ka value for this acid.   

(a)  Sketch a titration curve for the titration of 25.0 mL of 1.00 M NH3 with 0.25 M HCl. Indicate the pH corresponding to the equivalence point. 

(b)        Calculate the solubility in g L-1 for calcium fluoride, CaF2.

            [Ksp CaF2 = 3.2 x 10-11]     

                    Explain your answer.  

(d)  A 25.00 mL of 0.50 M acetic acid, CH3COOH solution is titrated with 0.50 M sodium hydroxide, NaOH solution. Calculate the initial pH of the acid solution. Qualitatively, predict the pH of the solution after the addition of 25.00 mL NaOH solution. Explain your answer.  Ka (CH3COOH) = 1.8 x 10-5] 

i.  Write the dissociation equation for the base and derive its dissociation constant expression.

ii.   Calculate the pH of a 0.4 M aqueous solution of the amine.

(b)  Sketch the curve for the titration of 30.0 mL of 0.10 M NaOH with 0.10 M HCl. Indicate the approximate pH at the beginning of the titration and at the equivalence point. What is the total volume of the solution at the equivalence point? 

(c)  The solubility product of lead (II) bromide, PbBr2 is 8.0 x 10-5 at room temperature. Determine the molar solubility of lead (II) bromide, PbBr2 in 0.10 M sodium bromide, NaBr solution.