Acid/base chemistry questions??

Question

1. B is a weak base. Which equilibrium corresponds to the equilibrium constant Ka for
HB+? (a) HB+ + H2O <==> B + H¬3O+
(b) HB+ + H3O+ <==> H2B2+ + H2O
(c) B + H2O <==> HB+ + OH-
(d) HB+ + OH- <==> B + H2O
(e) B + H3O+ <==> HB+ + H2O



2. What is the pH of a 0.015 M aqueous solution of barium hydroxide?
(a) 12.48 (b) 12.18 (c) 1.82 (d) 10.35 (e) 1.52


3. The solubility of lead (II) chloride (PbCl2) is 1.6 x 106-2 M. What is the Ksp of PbCl2?

4. The Ka of hypochlorous acid is 3.0 x 106-8 at 25. What is the % ionization of hypochlorous acid in a .015-M aqueous solution of HClO at 25?

5 .15-M aqueous solution of the weak acid HA at 25 degrees celcius has a pH of 5.35. What is the Ka value for HA?














If you could please explain your answer(s), that would be perfect!!
thanks!

Answer 1

1 (c) This is for a Bronsted base.
2. Ba(OH)2 totally dissociates so it would form a solution 0.03 M in OH-. The corresponding pOH is 1.52, so the pH= 12.48.
3. saturated PbCl2 would form 1.6x10-2 M Pb+2 and 3.2x10-2 M Cl2. Ksp = [Pb+2][Cl-]^2
4. ALWAYS write your equation
HOCl = H+ + OCl-
From this, (a) all H+ comes from the acid
(b) [OCl-] = [H+]
Call the conc of these ions X, so
X^2 / 0.015M-X = 3.0x10-8
Strictly you would solve the quadratic, but Chemists are lousy in algebra, so they neglect the X compared to 0.015 M, which is usually reasonable unless the acid is very dilute or the Ka is around 10-4 or higher. Then
X^2 = 4.5x10-10
X = 2.1x10-5
Percent ionization = 2.1x 100x10-5/1.5x10-2=0.14%

5. Convert pH to [H+]
Set up as above, however you MAY have to consider the "X" in the denominator that we dropped above.

Answer 2

i want to preface my answer through telling u that u can digital mail me with the different questions. that is difficult to respond to all 3 questions, yet ill attempt. a million. we see that H3O+ is the most pricey acid, because water is a very very weak base. thye conjugate of a good looking good acid is a weak base. the more advantageous the acid, the weaker its conjugate. the more advantageous the bottom, the weaker its conjugate. 2. i be conscious of for in simple terms about certain that B(OH)3 is an ACID. mainly, all nonmetal OH's are acids. if u rearrange this formula, u get H3BO3. i will say D. 3. to discover the pH of a weak acid, u take the sq. root of Ka x Molarity. on condition that all molarities are a million, take the sq. root of all the Ka's and take the damaging log of what u were given. and the nearest one to 7 is the winner. that is going to be the NH4+ i desire this enables.