a. What is the H+ concentration for an aqueous solution with pOH = 3.73 at 25 ?C
ID: 304311 • Letter: A
Question
a. What is the H+ concentration for an aqueous solution with pOH = 3.73 at 25 ?C?
Express the molar concentration numerically using two significant figures.
b. Arrange the following aqueous solutions, all at 25 ?C, in order of decreasing acidity.
pOH = 8.55, pH =5.45, 0.0018 M KOH, 0.0023 M HCl
Rank from most acidic to most basic.
c. At a certain temperature, the pH of a neutral solution is 7.33. What is the value of Kw at that temperature?
Express your answer numerically using two significant figures.
Explanation / Answer
a. POH = 3.73
PH = 14-POH
= 14-3.73
PH = 10.27
-log[H^+] = 10.27
[H^+] = 10^-10.27 =5.4*10^-11M
b. POH = 8.55
PH = 14-POH
= 14-8.55
= 5.45
KOH(aq) ---------------> K^+ (aq) + OH^- (aq)
0.0018M 0.0018M
[OH^-] = [KOH]
[OH^-] = 0.0018M
POH = -log[OH^-]
= -log0.0018
= 2.7447
PH = 14-POH
= 14-2.7447
= 11.2553
HCl(aq) --------------> H^+ (aq) + Cl^- (aq)
0.0023M 0.0023M
[H^+] = [HCl]
[H^+] = 0.0023M
PH = -log[H^+]
= -log0.0023
= 2.6382
0.0023MHCl>(POH =8.55) = (PH=5.45) > 0.0018 M KOH
c.
PH = 7.33
-log[H^+] = 7.33
[H^+] =10^-7.33 = 4.67*10^-8M
in neutral solution [H^+] = [OH^-] = 4.67*10^-8 M
Kw = [H^+][OH^-]
Kw = 4.67*10^-8M * 4.67*10^-8M = 2.2*10^-15M^2
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