Question

Find (H+), (OH-), and sthe pH of the following solutions.

A. 30.0 mL of a 0.216 M solution of HC diluted with enough water to make 125 mL of solution.

B. A solution made by dissolving 275 mL of HBr gas at 25 C and 1.00 atm in enough water to make 475 mL of solution., Assume that all the HBr dissolves in water.

Answer 1

A. M1V1 = M2V2

(30)(0.216) = (125)M2

M2 = 0.05184 M

[H+] = 0.05184

[OH-] = 10^(-14)/0.05184 = 1.929 * 10^(-13)

pH = -log[H+] = -log[0.05184] = 2 - log(5.184) = 1.285

B.

Using the ideal gas equation

PV = nRT

(1.00)(0.275) = n * 0.0821 * 298

n = 0.01124 moles

Molarity of solution = moles of solute/volume of solution(L)

=> 0.01124/(475/1000)

=> 0.02366 M

[H+] = 0.02366 M

[OH-] = 10^(-14)/0.02366 = 4.225 * 10^(-13)

pH = -log[H+] = -log[0.02366] = 2 - log(2.366) = 1.625