10. Which of the following description is correct? (4%)
(A) The solubility product constant (Ksp) of aluminum hydroxide (Al(OH)3) is 3 ×10-34; the Ksp of cadmium sulfide (CdS)is 1× 10-27. Based on this information, we know that Al(OH)3 is less soluble than CdS in pure water.
(B) A glass of aqueous solution (100 mL) contains [Ca2+] = 2.13✖10-4 M, [F-] = 4.26✖ 10 -4 M, and 0. 781 g of insolubleCaf2 solid. Based on this information, we can estimate the Ksp of Caf2 to be ~3.9 x 10-11
(C) Even through the same chemical can sometimes exist in more than one crystalline form, e.g., CaCO3 can be bothcalcite and aragonite, they are always equally soluble.
(D) The pKa1and pKa2 of methionine are 2.28 and 9.21. Based on this information, we know that methionine has thebest buffering power (capacity) at pH 5.75 (the mid-point between the two pKa values).
(E) The hydrogen cation concentration ([H+]) of a pH 6.5 solution is 5.0 ✖10-7 M.