This document provides examples of calculating the pH of various strong acid solutions, including nitric acid, perchloric acid, hydrochloric acid, a mixture of hydrochloric acid and hydroiodic acid, and a solution of bromoacetic acid that is partially ionized. It also asks questions about weak acids, Lewis acids, and which compounds form more acidic solutions based on cation properties.

1. KEY
GENERAL CHEMISTRY-II (1412)
S.I. # 24
Calculate the pH of each of the following strong acid solutions:
1. 0.00835 M HNO3
0.00835 M HNO3 = 0.0835 M H+; pH = -log(0.00835) = 2.08
2. 0.525 M HClO4
0.525 g HClO4 x 1 mol HClO4 = 2.612 x 10-3 = 2.61 x 10-3 M HClO4
2.00 L Soln 100.5 g HClO4
[H+] = 2.61 x 10-3 M; pH = -log (2.612 x 10-3) = 2.583
3. 5.00 mL of 1 M HCl diluted to 0.500 L
Mc x Vc = Md x Vd; 0.500 L = 500 mL
1.00 M HCl x 5.00 mL HCl = Md HCl x 500 mL HCl
Md HCl = 1.00 M x 5.00 mL = 1.00 x 10-2 M HCl = 1.00 x 10-2 M H+
500 mL
pH = - log (1.00 x 10-2) = 2.000
4. a mixture formed by adding 50.0 mL of 0.020 M HCl to 150 mL of
0.010 M HI.
[H+] total = mol H+ from HCl + mol H+ from HI ; mol = M x L
total L solution
[H+]total = (0.020 M HCl x 0.0500 L) + (0.010 M HI x 0.150 L)
0.200 L
[H+]total = 1.0 x 10-3 mol H+ + 1.50 x 10-3 mol H+ = 0.013 M
0.200 L
pH = -log (0.0125) = 1.90
5. A 0.100 M solution of brmoacetic acid (BrCH2COOH) is 13.2% ionized.
Calculate [H+] , [BrCH2COO-], and [BrCH2COOH].

2. KEY
[H+] = 0.132 x [BrCH2COOH]initial = 0.0132 m
BrCH2COOH (aq)  H+ (aq) + BrCH2COO- (aq)
Initial 0.100 M 0 0
Equil. 0.087 0.0132 M 0.0132 M
6. How many moles of HF (Ka = 6.8 x 10-4) must be present in 0.200 L to form a
solution with a pH of 3.25?
[H+] = 10-pH = [C2H3O2-] [HC2H3O2] = x – [H+].
Substitute into the Ka expression and solve for x. solve
[H+] = 10-pH =10-2.90 = 1.26x10-3 = 1.3x10-3 M
Ka = 1.8x10-5 = [H+][C2H3O2-] = (1.26 x 10-3)2
[HC2H3O2] (x-1.26x10-3)
1.8x10-5 (x – 1.26x10-3) = (1.26x10-3)2;
1.8x10-5 x = 1.585x10-6 + 2.266x10-8 = 1.608x10-6;
x = 0.08931 = 0.089 M HC2H3O2
7. What are tow kinds of molecules or ions that commonly function as weak bases?
Organic amines and anions that are the conjugate bases of weak acids function as weak
bases.
8. If a substance is a Lewis acid, is it necessarily a Bronsted-Lowery acid? Is it
necessarily an Arrhenius acid? Explain.
No. If a substance is a lewis acid, it is not necessarily a Bronsted or an Arrhenius acid.
Lewis acid is an electron pair acceptor which is not necessarily an H+ donor.
9. Which member of each pair produces the more acidic aqueous solution:
a. ZnBr2 or CdCl2 ZnBr2, smaller cation radius, same charge
b. CuCl or Cu(NO3)2 Cu(NO3)2, higher cation charge
c. Ca(NO3)2 or NiBr2 NiBr2, smaller cation radius, same charge