Question

The substance (CH_3CH_2)_2NH is considered Which one of the following pairs is not a conjugate acid-base pair? A solution is prepared by adding 0.10 mol of sodium fluoride, NaF. to 1.00 L of water. Which statement about the solution is correct? Which, if any, of the following aqueous mixtures would be a buffer system? Which of the following acids should be used to prepare a buffer with a pH of 4.5? Consider the dissolution of MnS in water (K_sp = 3.0 x 10^-14). How is the solubility of manganese(II) sulfide affected by the addition of aqueous potassium hydroxide to the system?

Answer 1

15)

this is diethyl amine; its a pretty common WEAK BASE since it won't ionize completely

16)

OH- and O2-

since O2- is not actually in solution

OH- may only gain H+, therefore its conjugate will be H2O not O-2

17)

The soluition is basic since

NaF --> Na+ and F-

F- + H2O <-> HF + OH-

18)

Buffer is a weak base/acid + conjugate acid/base respectively so:

none of these is the case

19)

for a pH = 4.5 choose a pKa = pH or nearest

or pOH = 14-4.5 = 9.5 or pKb = 9.5 or nearest

choose B since Ka = 1.8*10^-5 then pK a= -log(1.8*10^-5) = 4.7447

20)

Adding KOH will increase OH- ions, therefore the equilibrium will shift toward the reactants

the solubility will DECREASE since more solid product is favoured