Exercises in OpenStax Chemistry, Ch.14
Ryan Kilby
CHM/151
May 6, 2017
Dr. DANIEL GILBERT Week One Exercises in OpenStax Chemistry, Ch. 14 Chapter Fourteen
18. Calculate the pH and the pOH of each of the following solutions at 25 °C for which the
substances ionize completely:
(a) 0.200 M HCl
HCl = H+ + ClSubstances ionize completely results in
+ ¿¿
H
¿
−¿
Cl ¿
¿
¿ +¿¿
H
¿
¿
pH=−log ¿ (b) 0.0143 M NaOH
NaOH = Na+ + OHSubstances ionize completely results in
+¿
Na ¿
¿
−¿
OH ¿
¿
¿ −¿
OH ¿
¿
¿
pOH=−log¿
pH=14− pOH =14−1.84=12.16 (c) 3.0 M HNO3 HNO3 = H+ + HNO3Substances ionize completely results in
+¿¿
H
¿
−¿
N O 3¿
¿
¿
+¿¿
H
¿
¿
pH=−log ¿
(d) 0.0031 M Ca(OH)2
Substances ionize completely results in
−¿
OH ¿
¿
OH ¿2
mol
mol
Ca(¿)=2 ×0.0031
=0.0062
L
L
¿
−¿
OH ¿
¿
¿
pOH=−log¿
pH=14− pOH =14−2.21=11.79
36. What is the ionization constant at 25 °C for the weak acid (CH3)2 NH2 +, the conjugate
acid of the weak base
(CH3)2NH, Kb = 7.4 × 10−4?
+¿¿
H
¿
( C H 3 ¿2 NH ]
¿
+¿
C H 3 ¿2 N H ¿2
¿
¿
¿
¿
K i=¿ So we can also have
+¿
H 3 O¿
¿
( C H 3 ¿2 NH ]
¿
+¿
C H 3 ¿2 N H ¿2
¿
¿
¿
¿
K c =¿ 52. Which of the following will increase the percent of HF that is converted to the fluoride
ion in water?
(a) addition of NaOH
(b) addition of HCl
(c) addition of NaF
60. Calculate the ionization constant for each of the following acids or bases from the
ionization constant of its conjugate base or conjugate acid:
(a) F−
(b) NH4 +
(c) AsO4 3−
(d) (CH3)2NH2+
(e) NO2−
(f) HC2 O4 – (as a base)
78. Determine whether aqueous solutions of the following salts are acidic, basic, or neutral:
(a) Al(NO3)3
(b) RbI (c) KHCO2
(d) CH3NH3Br
90. What is [H3O+] in a solution of 0.075 M HNO2 and 0.030 M NaNO2?
HNO2(aq) + H2 O(l) ⇌ H3 O+(aq) + NO2 −(aq) Ka = 4.5 × 10−5 98. Calculate the pH of a buffer solution prepared from 0.155 mol of phosphoric acid, 0.250
mole of KH2PO4, and enough water to make 0.500 L of solution.
114. Draw a curve similar to that shown in Figure 14.23 for a series of solutions of NH3.
Plot [OH−] on the vertical axis and the total concentration of NH3 (both ionized and
nonionized NH3 molecules) on the horizontal axis.
Let the total concentration of NH3 vary from 1 × 10−10 M to 1 × 10−2 M. Reference
Rice University. (2015). OpenStax College. Retrieved from Rice University, Chemistry website.

 

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