# Acids Lesson 10 pH Calculations - PowerPoint PPT Presentation

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Acids Lesson 10 pH Calculations. pHEquations You must know the following equations, which are all based on the ionization of water at 25 0 C ! H 2 O ⇄ H + +OH - Kw =[H + ][ OH - ]= 1.00 x 10 -14 pH =-Log[H + ] pOH =-Log[OH - ] [H + ] =10 -pH [OH - ] =10 -pOH

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Acids Lesson 10 pH Calculations

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Acids

Lesson 10

pH Calculations

pHEquations

You must know the following equations, which are all based on the ionization of water at 250 C!

H2O⇄H++OH-

Kw=[H+][ OH-]=1.00 x 10-14

pH=-Log[H+]pOH=-Log[OH-]

[H+]=10-pH[OH-]=10-pOH

pH+pOH=pKw=14.000

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M

Calculation

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M

CalculationThe number of sig figs are 2 (green)

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M

CalculationpH = -Log[H+]

pH = -Log[2.5 x 10-4]

pH = 3.60The digit before the decimal does not count as a sig fig. Both digits after the decimal count for 2 sig figs.

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M3.60

CalculationpH = -Log[H+]

pH = -Log[2.5 x 10-4]

pH = 3.60keep all digits on the calculator- do not round!

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M3.60

CalculationpH + pOH = 14.00

3.60 + pOH = 14.00

pOH = 10.40

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M3.6010.40

Calculation[OH-]=10-pOH

[OH-]=10-10.40

[OH-]=4.0 x 10-11 M

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

CalculationNote that all of the entries in the last line have two sig figs!

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

9.435

CalculationpH + pOH = 14.000

9.435 + pOH = 14.000

pOH = 4.565

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

9.4354.565

Calculation[OH-]=10-pOH

[OH-]=10-4.565

[OH-]=2.72 x 10-5 M

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

2.72 x 10-5 M9.4354.565

Calculation[H+][OH-]=1.00 x 10-14

[H+][2.72 x 10-5 ]=1.00 x 10-14

[H+]=3.67 x 10-10 M

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

CalculationNote that all of the entries in the last linehave three sig figs!

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

2.6 x 10-4 M

CalculationpOH = -Log[OH-]

pOH = -Log[2.6 x 10-4]

pOH = 3.59

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

2.6 x 10-4 M3.59

CalculationpH + pOH = 14.000

pH +3.59 = 14.000

pOH = 10.41

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

2.6 x 10-4 M10.413.59

Calculation[H+]=10-pH

[H+]=10-10.41

[H+]=3.8 x 10-11 M

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

3.8 x 10-11 M2.6 x 10-4 M10.413.59

CalculationNote that all of the entries in the last line have two sig figs!

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

3.8 x 10-11 M2.6 x 10-4 M10.413.59

8.40

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

3.8 x 10-11 M2.6 x 10-4 M10.413.59

4.0 x 10-9 M8.40

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

3.8 x 10-11 M2.6 x 10-4 M10.413.59

4.0 x 10-9 M8.40

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

3.8 x 10-11 M2.6 x 10-4 M10.413.59

2.5 x 10-6 M4.0 x 10-9 M8.40

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

3.8 x 10-11 M2.6 x 10-4 M10.413.59

2.5 x 10-6 M4.0 x 10-9 M5.608.40

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40

3.67 x 10-10 M2.72 x 10-5 M9.4354.565

3.8 x 10-11 M2.6 x 10-4 M10.413.59

2.5 x 10-6 M4.0 x 10-9 M5.608.40

CalculationNote that all of the entries in the last line have two sig figs!

pHCalculations

[H+][OH-]pHpOH

2.5 x 10-4 M4.0 x 10-11 M3.6010.40 acid

3.67 x 10-10 M2.72 x 10-5 M9.4354.565basic

3.8 x 10-11 M2.6 x 10-4 M10.413.59basic

2.5 x 10-6 M4.0 x 10-9 M5.608.40acid

If the pH is lower than 7, the solution is acidic!

If the pH is greater than 7, the solution is basic!

1.Calculate the pH of 0.40 M HI.

HIH++I-

0.40 M0.40 M0.40 M

pH = -Log[H+]

pH = -Log[0.40]

pH = 0.40

2.Calculate the pH of 0.030 M Ba(OH)2.

Ba(OH)2Ba2++2OH-

0.030 M0.030 M0.060 M

pOH = -Log[OH-]

pOH = -Log[0.060]

pOH = 1.22

pH + pOH = 14.000

pH +1.22 = 14.000

pH = 12.78

3.Calculate the pH of 100.0 mL of 1.0 M HCl after 300.0 mL of water is added to it.

HClH++Cl-

1001.0M

4000.25M0.25M

pH=0.60