Chemistry is pHun! pH and pOHThis is Sooo Basic!

pH pH ScalScal

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pH and pOH

pH = “power” of Hydrogen H+ Molarity

pH use H+ M as 10-x pH = - (-x) = x

pOH use OH- M as 10-x pOH = -(-x)= x

Chemistry is pHun!

pOH = “power” of Hydroxide OH- Molarity

pure water is neutral; that is, it ionizes in such a manner that : Molarity of H+ = Molarity of OH- = 10-7 M

H20 H+ + OH-

pH > 7.00 is basic

pH < 7.00 is acidicpH Scale:

goes from 0 → 14 pH = 7.00 is neutral

pH + pOH = 14

1. Examine the formula of the compound. If the compound has H+ in the formula then that solution is an acid. This will give you the pH. If the compound has OH in it then that compound is a base and will give you the pOH.

2. Next write the concentration (Molarity) as a “power of ten as 1 x 10-X X = # of decimal places.

3. The positive number for X will be the pH if an acid or pOH if a base. Find the other by subtracting the one you found from 14. pH + pOH = 14.

Steps To Finding pH & pOH:

Determine the pH and pOH of: a. 0.001 M HNO3

b. 0.00001 M HCl

a. 0.001 M H+ = 1 x 10-3 M H +

b. 0.00001 M H+ = 1 x10-5 M H+

pH= 3

pOH = 9

pOH = 11

pH= 5

Practice What is the pH ( and pOH) of a solution with[H+] of:

a) 0.000000000001 Mb) 0.000001 Mc) 0.000000001 M

pH = 12a) 1 x 10-12 = [H+]

pOH = 14 – pH = 2

b) 1 x 10-6 = [H+] pH = 6

pOH = 14 – pH = 8

pH = 9c) 1 x 10-9 = [H+]

pOH = 14 – pH = 5

Practice

Determine the pH (and pOH) for the following solutions:

a) 1.0 x 10-5 M HNO3

b) 1.0 x 10-6 M KOH

a) 1.0 x 10-5 = [H+] HNO3

pH = 5

pOH = 14 – pH = 9

b) 1.0 x 10-6 = [OH-] KOH

pOH = 6

pH = 14 – pOH = 8

Practice Problems:

Find the pH and pOH of these items:

1. Orange Juice H+ = 0.0001 M2. Vinegar H+ = 0.001 M3. Black Coffee H+ = 0.000001 M4. Ammonia H+ = 0.00000000001 M5. Baking Soda H+ = 0.000000001 M6. Stomach Acid H+ = 0.1 M

Practice Problems:

Find the pH and pOH of these items:

1. H+ = 1 x 10-4 M pH = 4 pOH = 102. H+ =1 x 10-3 M pH = 3 pOH = 113. H+ = 1x 10-6 M pH = 6 pOH = 84. H+ = 1 x 10-11 M pH = 11 pOH = 35. H+ = 1 x 10-8 M pH = 8 pOH = 66. H+ = 1 x 10-1 M pH = 1 pOH = 13

Practice Problems:

Find the pH and pOH of these solutions:

1. OH- = 0.0001 M2. OH- = 0.001 M3. OH- = 0.000001 M4. OH- = 0.00000000001 M5. OH- = 0.000000001 M6. OH- = 0.1 M

Practice Problems:

Find the pH and pOH of these solutions:

1. OH- = 1 x 10-4 M pOH = 4 pH = 102. OH- = 1 x 10-3 M pOH = 3 pH = 113. OH- = 1 x 10 -6 M pOH = 6 pH = 84. OH- = 1 x 10-11 M pOH =11 pH = 35. OH- = 1 x 10-9 M pOH = 9 pH = 56. OH- = 1x 10-1 M pOH = 1 pH = 13

Quiz

Determine the pH and pOH for the following solutions:

a) 0.00001 M CsOH

b) 0.01 M HF

Quiz

Determine the pH and pOH for the following solutions:

a) 0.00001 M CsOH 1 x 10-5 pOH = 5 pH = 9

b) 0.01 M HF 1 x 10-2 pH =2 pOH =12