Page 1318 - Chemistry--atom first
P. 1318
1308 Answer Key
[OH−] = 1.9 10−4 M [H3O+] = 5.3 10−11 M
75. 77.
79. (a) acidic; (b) basic; (c) acidic; (d) neutral 81.[H3O+] and are practically equal
83. [C6H4(CO2H)2] 7.2 10−3 M, [C6H4(CO2H)(CO2)−] = [H3O+] 2.8 10−3 M, 3.9 10−6 M, [OH−] 3.6 10−12 M
85.(a)
(b)
(c)
Solving for x gives 1.5 10−11 M. Therefore, compared with 0.014 M, this value is negligible (1.1
87. Excess H3O+ is removed primarily by the reaction:
10−7%).
Excess base is removed by the reaction:
89. [H3O+] = 1.5 10−4 M 91. [OH−] = 4.2 10−4 M 93. [NH4NO3] = 0.36 M
95. (a) The added HCl will increase the concentration of H3O+ slightly, which will react with and produce CH3CO2H in the process. Thus, decreases and [CH3CO2H] increases.
(b) The added KCH3CO2 will increase the concentration of which will react with H3O+ and produce CH3CO2 H in the process. Thus, [H3O+] decreases slightly and [CH3CO2H] increases.
(c) The added NaCl will have no effect on the concentration of the ions.
(d) The added KOH will produce OH− ions, which will react with the H3O+, thus reducing [H3O+]. Some additional CH3CO2H will dissociate, producing ions in the process. Thus, [CH3CO2H] decreases slightly and
increases.
(e) The added CH3CO2H will increase its concentration, causing more of it to dissociate and producing more
and H3O+ in the process. Thus, [H3O+] increases slightly and increases. 97. pH = 8.95
99. 37 g (0.27 mol)
101. (a) pH = 5.222;
(b) The solution is acidic. (c) pH = 5.221
103. To prepare the best buffer for a weak acid HA and its salt, the ratio should be as close to 1 as possible + +−3.1 −4
for effective buffer action. The [H3O ] concentration in a buffer of pH 3.1 is [H3O ] = 10 We can now solve for Ka of the best acid as follows:
= 7.94 10 M
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