Chem 1721/1821
Name _______________________________
Quiz 7 (20 points)
April 18, 2013
pX = −log X
pKw = pH + pOH
!=
Kw = 1 x 10—14 at 25ºC
pKw = pKa + pKb
!!± ! ! !!"#
!" = !! ! + !"#
!"
[!"#$]
[!"#$]
1.
Write the chemical equation for the solubility equilibrium of lead (II) iodide:
2.
A sparingly soluble salt, M3X4 is composed of a metal cation (M4+), and a nonmetal anion (X3—). What is the
mathematical relationship between Ksp and molar solubility (x) for this salt? Circle the one best answer below.
Ksp = 12x7
3.
a.
Ksp = 144x12
Ksp = 6912x7
Ksp = x2
Ksp = 432x5
Ksp = 2304x7
Calculate the solubility (in g/L) of cadmium iodate in water. For Cd(IO3)2, Ksp = 2.3 x 10—8; molar mass = 462.2
g/mol.
_____________________
b.
Calculate the molar solubility (in mol/L) of Cd(IO3)2 in 1.02 M KIO3 (aq).
_____________________
4.
Solid scandium fluoride is added to water and allowed to stand until equilibrium is established. This saturated solution
is then analyzed and found to have [Sc3+] = 2.0 x 10—5 M.
a.
Determine [F—] in this solution.
_____________________
b.
Determine Ksp for ScF3.
_____________________
5.
Show a calculation to determine if CaSO3 will precipitate when 250.0 mL of 4.4 x 10—4 M Ca(NO3)2 (aq) is mixed with
450.0 mL of 2.8 x 10—3 M Na2SO3 (aq). For CaSO3, Ksp = 6.8 x 10—8.
6.
The dissolution of silver nitrite (AgNO2, Ksp = 6.0 x 10—4) is endothermic. Circle all of the things below that should
result in increased solubility for AgNO2.
add NaOH(aq)
increase [H+(aq)]
use AgNO3(aq) as solvent instead of H2O (l)
increase temperature
add more AgNO2 (s)
add Na2S2O3 (aq) – for Ag2(S2O3)23—, Kf = 2.9 x 1013
7.
For copper (II) carbonate (CuCO3), Ksp = 1.4 x 10—10. When NH3 (aq) is added to a saturated solution of copper (II)
carbonate, the complex ion Cu(NH3)42+ (Kf = 1.1 x 1013) forms. Write the overall chemical equation that describes what
is happening in this experiment, and calculate the equilibrium constant (Kc) for the reaction.
equation: _______________________________________________________________
8.
Kc = ___________________
A buffer solution is prepared by combining 1.26 M C5H5N (aq) and 1.42 M C5H5NHBr (aq). For pyridine, C5H5N,
Kb = 1.5 x 10—9.
a. Determine the pH of this buffer solution.
pH = _________________
b.
Determine the pH of this solution after the addition of 0.124 mol HClO4 (aq) to 500.0 mL of the buffer solution.
pH = _________________
c.
9.
After this addition of acid, has the buffer failed?
Yes
or
No
Determine the pH at the stoichiometric point in the titration of 40.0 mL of 0.775 M HC3H5O3 (Ka = 1.3 x 10—4) with
0.505 M KOH (aq).
pH = _________________