Chemistry 162. Test Three. April 09, 2014. Name ________________________________________________
Part One. Twenty three points (each question is two points)
_____ 1) An 0.10 M solution of a weak acid has a pH of 2.30. What is the Ka for this acid?
a- 5.0 x 10-2
b- 5.0 x 10-3
c- 2.5 x 10-4
d- 2.5 x 10-5
_____ 2) Which of the following is true for an 0.1 M solution of a weak acid?
a- [HA] > [A-]
b- [A-] = 0.10 M
c- pH = 1.0
d- [H3O+] = 0.10 M
_____ 3) Which of the following mixtures will be a buffer when dissolved in one liter of water?
a- 0.10 mol Ca(OH)2 and 0.30 mol HI
b- 0.40 mol NH3 and 0.40 mol HCl
c- 0.20 mol H3PO4 and 0.10 mol NaOH
d- 0.20 mol HBr and 0.10 mol NaOH
_____ 4) Which of the following statements is/are true for the titration of a weak acid with a strong base?
I- At the equivalence point the pH is 7.
II - The moles of acid equals the moles of base at the equivalence point.
III – At the equivalence point the pH is equal to the pKa
a- II and III only
b-II only
c- I and II only
d- III only
_____ 5) What is the solubility product expression for Bi2S3?
a- [Bi2+][S2-]3
b- [Bi2][S3]
c- [2Bi3+]2[3S2-]3
d-[Bi3+]2[S2-]3
_____ 6) What is the pH of a saturated solution of Mg(OH)2?
a- 3.28
b- 10.93
c- 9.40
d- 10.73
_____ 7) 0.10 moles of NaOH is added to one liter of a 0.30 M solution of acetic acid. Ignoring any volume change, what
is the pH of the new solution.
a- 4.44
b- 2.63
c- 4.74
d- the pH cannot be determined from the information given
_____ 8) Which of the following will not increase the solubility of Ag3AsO4?
a- lowering the pH
b- addition of NH3
c- adding additional silver arsenate
d- increasing the solution temperature
_____ 9) For the following pairs – H2S and PH3 – HClO2 and HClO3 – the stronger acids are
a- PH3 and HClO3
b- H2S and HClO3
c- H2S and HClO2
d- PH3 and HClO2
_____ 10) What is the conjugate base for H3AsO4?
a- H4AsO4+
b- HAsO42c- AsO43d- H2AsO4-
Part Two.
1) (9 points) Definitions.
Buffer
Ka
Buffer capacity
2) (7 points) What is the pH of a 2.3 x 10-2 M solution of pyruvic acid?
3) (7 points) What is the pH of a 0.100 M solution of N2H4?
4) (9 points) What is the molar solubility of Al(OH)3? What is the solubility in g/L?
5) (10 points) A solution is initially 0.200 M in Fe2+. What is the concentration of the Fe2+ if CN- is added so that [CN-] =
6.0 M?
6) (10 points) From our table, what acid would be best to prepare a buffer at a pH of 5.34? Why? If we make the buffer
such that [A-] = 0.450 M, what would be the concentration of the HA ([HA] = ??).