pH scale

1
(No Transcript)
2
(No Transcript)
3
pH scale

• Logarithmic scale
• expressing H1 concentration, H1
• If pH changes by factor of 1,
• H1 changes by factor of 10
• pH -logH1

4
(No Transcript)
5
Molarity to pH

• To determine pH
• Express H1 in scientific notation
• Remember, means concentration of whatever
  is inside brackets
• The log is the power of 10

6
Molarity to pH for Pure water

• Theres a tiny bit of ionization
• H2O ? H1 OH-1
• H1 OH-1 1 X 10-7 M
• pH -logH1 -(-7) 7

7
pH
8
(No Transcript)
9
pH to Molarity

• pH -logH1, solve for H1
• -pH logH1
• Antilog(-pH) H1
• Say pH 5, then pH -5
• Antilog(-5) 10-5
• The pH becomes the power of 10!

10
pOH

• By analogy pOH is defined as logOH-1
• Express OH-1 in scientific notation
• If OH-1 1.0 X 10-3 M
• Then pOH -log(10-3) -(-3) 3

11
pH pOH 14

• pH 3, pOH
• pH 7, pOH
• pH 10, pOH
• pH 9, pOH
• pH 1, pOH

7
12
(No Transcript)
13
ACID or BASE?

• Acids H1 ? OH-1
• Bases OH-1 ? H1

14
(No Transcript)
15
pH range

• 0 to 14
• with 7 being neutral
• pH 0, strongly acidic
• pH 14, strongly basic

16
If pH 4

• H1 ?
• pOH ?
• OH-1 ?

17
If the OH-1 1 X 10-3
pOH -logOH-1 -log(10-3) -(-3) 3

• pOH ?
• pH ?
• H1 ?

18
If the H1 1 x 10-5 M

• The pH ?
• The pOH ?
• The OH- ?

19
(No Transcript)
20
How to safely test pH

• Instruments use a pH meter
• Indicators use a series of indicators
• See if the substance reacts with a metal other
  than Cu, Ag, or Au
• NEVER taste

21
(No Transcript)
22
Indicator

• substance that changes color over narrow pH range
• Use several indicators to narrow down pH range of
  substance

23
(No Transcript)
24
(No Transcript)