Exam 16: Additional Aqueous Equilibria: Chemistry and the Oceans

Let s be the number of moles of lithium phosphate (Li₃PO₄) that dissolve in water to make exactly 1 L of solution. (1) Write the solubility product expression for lithium phosphate in terms of s. (2) Calculate a value for K_sp given that s  3.30  10^3M.

Dissolved concentrations of copper(II) as low as 10^6 M are toxic to phytoplankton. However, phytoplankton survive in a solution that is 10^3 M in copper(II) nitrate and 10^3 M ethylenediaminetetraacetic acid (EDTA). Why?

A mining operation needs to separate silver and copper. You are hired as a summer intern in a beautiful Colorado mining town, and one of your tasks is to determine whether this separation can be accomplished by oxidizing the metals to Ag^ and Cu^, each one at a concentration of 0.15 M, and then precipitating one as the chloride salt without precipitating the other. AgCl precipitates first. What is the concentration of the Ag^ remaining in solution when CuCl begins to precipitate? For AgCl, pK_sp  9.74, and for CuCl, pK_sp  6.76.

Glycolic acid, which is a monoprotic acid and a constituent in sugar cane, has a pK_a of 3.9. A 25.0 mL solution of glycolic acid is titrated to the stoichiometric point with 35.8 mL of 0.020 M sodium hydroxide solution. What is the pH of the resulting solution at the stoichiometric point?

A phosphate buffer solution (25.00 mL sample) used for a growth medium was titrated with 0.1000 M hydrochloric acid. The components of the buffer were sodium monohydrogen phosphate and sodium dihydrogen phosphate. The first endpoint occurred at a volume of 10.32 mL, and the second occurred after an additional 18.62 mL was added, for a total volume of 28.94 mL. What was the total concentration of phosphate (in any form) in the buffer?

What is the pH of a solution containing 0.30 M lactic acid and 0.50 M of lactate ion (K_a for lactic acid  1.38  10^4)?

Identify all the correct statements about an acid-base buffer solution. I. It can be prepared by combining a strong acid with a salt of its conjugate base. II. It can be prepared by combining a weak acid with a salt of its conjugate base. III. It can be prepared by combining a weak base with its conjugate acid. IV. The pH of a buffer solution does not change when the solution is diluted. V. A buffer solution resists changes in its pH when an acid or base is added to it.