p105-06 Solutions

 

Exercises

1.         Calculate the pH of the following if [H+] = :

( remember 416's for H only, M = mole/L = g/L)

a.         0.0010 M

pH = -log(0.001) = 3.0

b.         0.000001 M

6

c.         0.002 M

2.7

d.         10-11 M

11

e.         0.00025 M

3.6

2.         Which of the above (in #1) are acids?

All except d

3.         How much more acidic is a pH 4 solution compared to a pH = 6 solution?

10-4/10-6 = 100 x more acidic

4.         How much more basic is a pH 11 solution compared to a pH = 9 solution?

100 x more

5.         If 0.0044 g of H+ are dissolved in 500 mL of solution, what is the pH of that solution?

pH = -log([0.0044g/1]/0.500L) = 2.1

6.         a.         List three everyday solutions or substances with a pH < 7.

Coke, apple juice, toilet bowl cleaner, wine, stomach acid

            b.         Do the same for pH > 7.

Baking soda, ocean water, windex

 

Exercises for*430 Section on [OH-1] [H+1] = 10-14

 

7.         The pH of a solution changes from pH 10 to pH 7 after neutralization.

 

What is the molar concentration of the hydroxyl ions [OH-] and hydrogen ions [H+] of the final solution?

 

Justify your answer.

 

At pH = 7,  [OH-] = [H+], so [H+] = 10-pH = 10-7 M = [OH-]

 

8.         A solution of potassium hydroxide, KOH, has a pH of 13.

 

What is the hydroxide ion, OH-, concentration of this KOH solution?

 

Show all your work.

[H+] =10-pH = 10-13 M

[OH-] = 10-14/10-13 =­10-1 M

           

9.         A bottle containing an unknown solution has been found with a label which reads «pH 4».  What is the OH- ion concentration of this solution?

[H+] =10-pH = 10-4 M

[OH-] = 10-14/10-4 =­10-10 M

 

10.        The table below describes six different solutions.  Six pH values are given as well as different concentrations of H+ and OH- ions for these solutions.

 

In which group of solutions below has the pH been correctly identified?

 

 

Solutions

 

pH

 

Concentration of

Ions H+

 

Concentration of

Ions OH-

 

a

 

2

 

 

 

1 ´ 10-12

 

b

 

7

 

1 ´ 10-7

 

 

 

c

 

4

 

1 ´ 10-10

 

 

 

d

 

5

 

 

 

1 ´ 10-9

 

e

 

8

 

1 ´ 108

 

 

 

f

 

1

 

 

 

1 ´ 10-14

 

 

A)

 

Solutions a, b and d

 

B)

 

Solutions a, b and e

 

C)

 

Solutions c, d and f

 

D)

 

Solutions c, e and f

 

 

11.        The table below contains different solutions, their pH values and the different concentrations of H+ ions and OH- ions associated with them

 

 

SOLUTIONS

 

pH

 

IONS H+

 

IONS OH-

 

a

 

2

 

 

 

10-12

 

b

 

7

 

10-7

 

 

 

c

 

4

 

10-10

 

 

 

d

 

5

 

 

 

10-9

 

e

 

8

 

108

 

 

 

f

 

1

 

 

 

10-14

 

For which of the above solutions is the information provided incorrect? c,e, and f

 

 

12.        A certain soft drink has a pH of 3.  What quantity of H+ ions and OH- ions would you consume if you drank one litre of this soft drink?

 

            [H+] =10-pH = 10-3 M

[OH-] = 10-14/10-3 =­10-11 M

                       

                        in one litre of soft drink, there are 10-3 moles = 10-3 g of H+

                                and ­10-11 moles of OH- = 10-11 X 17g/mole = 1.7 X10-10 g of OH-