# What is pH? - PowerPoint PPT Presentation

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What is pH?. Concentration and hydrogen ions and hydroxide ions are a measure of The acidity and alkalinity of a solution. How was the concept of pH developed?. H 2 O is a molecule. Therefore, pure water does not conduct electricity. Or does it?.

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What is pH?

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## What is pH?

Concentration and hydrogen ions and hydroxide ions are a measure of

The acidity and alkalinity of a solution.

### How was the concept of pH developed?

H2 O is a molecule.

Therefore, pure water does not conduct electricity.

### Or does it?

When pure water was found to conduct very small currents of electricity, the self-ionization of water was discovered.

### Self-ionization of water

H2 O  H+ + OH-

Water can dissociate into Hydronium ions and hydroxide ions.

### How much dissociation is there?

[H+] = 1 x 10-7 M

[OH-] = 1 x 10-7 M

Therefore:

[H+] x [OH-] = 1 x 10-14 M

### [h+]x [OH-] = 1 x 10-14 M

Is called the

Ion-product constant

AKA: kw

Kw = 1 x 10-14 M

### acidity is a measure of the [H+] of a solution.

If the [H+] of a solution is 1.0 x 10-5M, is the solution acidic, basic or neutral?

1.0x 10-5 M is greater than 1.0 x 10-7 M

Therefore the solution is acidic

### Practice: acidic, basic or neutral?

• [H+] = 6.0 x 10-10M

• [H+] = 2.0 x 10-7 M

• [OH-] = 1.0 x 10 -7 M

### Solve these problems usingkw = [H+] x [OH-] and determine whether solution is acidic, neutral or basic

• [OH-] = 1 x 10-3

2. [OH-] = 2.0 x 10-11

3. [OH-] = 3.5 x 10-7

### The pH scale

Ranges from 0 -14.

0 – 6.9 = acidic

7.0 = neutral

7.1 – 14.0 = basic (alkaline)

### So where do these numbers come from?

pH = - log [H+]

That’s where they come from!

### What is the pH?

• [H+] = 1.0 x 10-4 M

• [H+ ] = 1.0 x 10 -2 M

• [H+] = 1.0 x 10 -10 M

• [H+] = 1.0 x 10-7 M

• [H+] = 1.0 x 10-14 M

• 4

• 2

• 10

• 7

• 14

### Get your calculators out and practice.

• [H+] = 0.0045 M

• [H+] = 8.7 x 10-6 M

• [H+] = 0.0015M

• [H+] = 1.2 x 10-3 M

• PH = 2.35

• PH = 5.06

• PH = 2.82

• PH = 2.92

### Find the pH and determine if it is acid basic or neutral

• [H+] = 1.5 x 10-9

• [H+] = 3.4 x 10-2

• [H+] = 5.5 x 10-11

• [H+] = 1.0 x 10-7

### You can also calculate ph from [OH- ]

If you are given [OH-] use [H+] = 1 x 10-14

[OH-]

To find hydrogen ion concentration then solve for pH

pH = –log [H+]

### Let’s practice

Calculate the pH of a solution with a [OH-] of 3.5 x 10-9

### Exit Slip: Your Name here……

• Find the pH of a solution with an hydroxide concentration of [OH-] = 2.9 x 10-5

2. A solution has a hydrogen ion concentration of

[H+] = 5.0 x 10 -12. Is it acidic, basic or neutral?