1. Lesson 19
Temperature
and pH

3. Kw and Temperature
Energy H2O ⇋ H+ + OH-
@ 25 oC Kw = 1.0 x  
Higher Temperatures
@ 50 oC
shifts right
Kw > 1.0 x
pH < 7
[H+] > 1.0 x M
pOH < 7
[OH-] > 1.0 x M
@ this temperature pH + pOH = pKw < 14

4. Kw and Temperature
Energy H2O ⇋ H+ + OH-
@ 25 oC Kw = 1.0 x  
Lower Temperatures
shifts left
Kw < x
pH > 7
[H+] < x M
pOH > 7
[OH-] < x M
@ this temperature pH + pOH = pKw > 14

5. Important Points If you're not @ 25oC [H+][OH-] ≠ 1.0 x 10-14
pH + POH ≠ 14
All other equations are valid and…….
Pure water is always neutral, but pH ≠ 7 and…….
[H+] = [OH-] and ……
pH = pOH

6. Is the temperature higher or lower than 25 oC? Calculate the Kw.
The pH of pure water is 6.50
Is the temperature higher or lower than 25 oC?
Calculate the Kw.
Energy + H2O ⇋ H+ + OH-
Higher
[H+] = = x M
[OH-] = x M
Kw = [H+][OH-] = ( x 10-7)2
Kw = 1.0 x
Is water acidic, basic or neutral?
neutral

7.  2. The Kw = 5.0 x 10-13 for pure water.
Is the temperature higher or lower than 25 oC?
Calculate the pH , POH, and pKw.
Energy + H2O ⇋ H+ + OH-
Kw > x
shifted right……
temperature is higher
Kw = x = [H+][OH-] = x2
x = [H+] = x M
pH = pOH = 6.15
pKw =
Is water acidic, basic or ?
neutral

8. 3. 25. 0 ml of 0. 100 M NaOH, 10. 0 mL 0. 200 M KOH, and 20. 0 mL of
ml of M NaOH, 10.0 mL M KOH, and mL of M H2SO4 are poured into the same beaker. What is the resulting pH?
L x mole NaOH = mol L
L x mole KOH = mol
Total = mol
L x mole H2SO4 = mol

9. 2XOH + H2SO4 → X2SO4 + 2HOH
I mol mol
C mol mol
E mol
Total Volume = mL mL mL = mL
Molarity = mol = M L
pOH = 2.04 pH =