Question

1. Calculate the molarity of hydroxide ion in an aqueous solution that has a pOH of 7.55.

	6.5 ⋅ 10-14
	6.45
	3.5 ⋅ 10-7
	7.6 ⋅10-14
	2.8 ⋅ 10-8

2. What is the pH of an aqueous solution at 25.0 °C that contains 3.98 ⋅ 10^-9 M hydronium ion?

	8.400
	3.980
	7.000
	9.000
	5.600

3. If the pOH for a solution is 3.00, what is the pH?

part b: Is the solution acidic or basic?

	basic
	neutral
	acidic

4. Which solution will be the most basic?

	0.20 M CsOH
	0.20 M NH4OH
	0.20 M Ca(OH)2
	0.20 M KOH
	All solutions have equal basicity.

5. A 6.0 ⋅ 10^-3 M aqueous solution of Ca(OH)2 at 25.0 °C has a pH of ________.

	11.78
	8.3 ⋅ 10-13
	1.2 ⋅ 10-2
	1.92
	12.08

Answer 1

1)

pOH = 7.55

[OH-] = 10^-pOH = 10^-7.55

[OH-]   = 2.8 x 10^-8 M --------------------> answer

2)

[H3O+] = 3.98 x 10^-9 M

pH = -log [H3O+]

pH = -log (3.98 x 10^-9)

pH = 8.400 ----------------------> answer

3)

pOH = 3

pH + pOH =14

pH = 11

pH >7 so it is basic ----------------> answer

4)

most basic 0.20 M Ca(OH)2

because OH- concentration = 2 x 0.2 = 0.4 M

5)

Ca(OH)2 = 6 x 10^-3 M

[OH-] = 2 x 6 x 10^-3 = 0.012 M

pOH = -log [OH-] = 1.92

pH + pOH = 14

pH = 12.08 ------------------> answer