Chemistry 2000, Section A
Spring 1996 Test 3

All questions are equally weighted.

1. Lactic acid is a monoprotic acid with a of 3.86 and a molar mass of 74.079g/mol. What is the pH of a solution made by dissolving 50g of lactic acid in 1L of water?
2. The single dissociable proton of benzoic acid (molar mass 122.123g/mol) has a of 4.2. Benzoic acid and sodium benzoate (the sodium salt of the conjugate base, molar mass 144.11g/mol) are both solids at room temperature. What masses of benzoic acid and of sodium benzoate would you have to dissolve in 1L of water to obtain a pH4.5 buffer with a total concentration (acid + conjugate base) of 0.3mol/L?
3. The solubility product of calcium fluoride is and its molar mass is 78.08g/mol. What is the solubility of calcium fluoride in g/L?
4. The equilibrium constant for the process

   

   is at physiological temperature (310K). If 10g of lactose (molar mass 342.299g/mol) is dissolved in 100mL of water, what are the equilibrium concentrations of glucose, galactose and lactose?

5. 10g of iron (specific heat capacity 0.444JK g ) at 300 C is plunged into a large quantity of water at its boiling point. How much water evaporates? The heat of vaporization of water is 40.79kJ/mol.