5. Sodium benzoate is the conjugate base of benzoic acid and it is used as a food preservative. How would you make a buffer solution based on this system to have a pH = 5.0? 6. What part of the titration curve of a weak acid corresponds to the buffer region? Explain. 7. Calcium carbonate is sparingly soluble in neutral water. Write out the equation for what is involved. Why doesn't an increase in the quantity of calcium carbonate increase its solubility? What units are solubilities measured in? 8. Consider the slightly soluble salt Pbl2. a) It is found that the solubility of PbI2 is 1.2 X 10-3 mole per liter at 298 K. What is the Ksp for Pbl2? b) What is the solubility of PbI2 in a 1.0 x 10-2 M Pb(NO3)2 solution? (If you do not obtain a Ksp for part (a), assume that Ksp = 1.0 x 10-10.) c) What do you think will happen to the solubility of Pbl2 in part (a) if the temperature is increased? What data would you need, to be sure of your answer?