Wake-upWrite down each equation below. Identify the base (B), acid (A), conjugate acid (CA), and conjugate base (CB).

1. NH3 + HCN NH4 + CN

2. HSO4 + PO4 HPO4 + SO4

3. HCO2H + OH H2O + CO2H

pH and pOH

Ways to measure Acidity/Basicity What is pH?

What is pOH?

What does pH represent?

Parts Hydrogen

pH

Measurement that reveals if a solution is acidic or basic

What is the pH Scale?

Runs from 0.0 to 14.0 with 7.0 being neutral; Logarithmic

pH scale

1 1476 8

Acid Base (Alkaline)

Neutral

Logarithmic Scale

A ten-fold difference between each successive full

number on the scale

Logarithmic Scale – ACID

Each whole pH value BELOW 7 is ten times more acidic than the next higher value. For example, pH 4 is ten times more acidic than pH 5 and 100 times

(10 times 10) more acidic than pH 6.

Logarithmic Scale: BASE

Each whole pH values ABOVE 7 is ten times more basic than the next lower whole value. For example, pH 10 is ten times more alkaline than pH 9 and 100

times (10 times 10) more alkaline than pH 8.

Basic Equations (Reference Table)

pH = -log[H+]

pOH = -log[OH-]

pH + pOH = 14

[H+] = 10-pH

[OH-] = 10-pOH

Example #1

What is the pH of a 0.031 M HCl solution?

Known = 0.031 M HClUnknown = pH

pH = -log[H+]

pH = -log [0.031M]

pH = 1.5

Example #2

What is the pH of a 2.50 x 10-6 M HNO3 solution?

Known = 2.50 x 10-6 M HNO3

Unknown = pH

pH = -log[H+]

pH = -log [2.50 x 10-6 M]

pH = 5.60

Example #3What is the pH of a 0.025 M NaOH solution?

Known = 0.025 M NaOHUnknown = pH

pOH = -log[OH+]

pOH = -log [0.025 M] = 1.6 pOH

pH = 12.4 pH + pOH = 14

pH + 1.6 = 14

Example #4What is the pH of a 0.000051 M NaOH

solution?

Known = 0.000051 M NaOHUnknown = pH

pOH = -log[OH+]

pOH = -log [0.000051 M] = 4.3 pOH

pH = 9.7

pH + pOH = 14

pH + 4.3 = 14

Calculating pOH • pOH = 14 – pH• pOH = -log[OH-]

EXAMPLE: What is the pOH of a solution that has a hydroxide ion concentration of 4.82 x 10-5 M ?

pOH = - log [OH-]

pOH = - log [4.82 x 10-5]

pOH = 4.32

YOU TRY! • Find the pH of the solution if [H+] = 1 x 10-4 M

• What is the hydrogen ion concentration if pH = 7.1?

• What is the pH if [OH-] = 4 x 10 -11 M?

pH = 4

7.1 = -log [H+]10 – 7.1 = [H+] = 7.9 x 10-8 M

pOH = -log [OH-]pOH = -log [4 x 10 -11 ] =

pH scale

1 1476 8

Acid Base

Strong Acid

Strong Base

Weak Acid

Weak Base

Neutral

Breakdown of water