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Backwards problem

Backwards problem. What is the [H 3 O + ] and [OH - ] and pOH of a solution with a pH of 8.7? 8.7 = -log [H 3 O + ] -8.7 = log [H 3 O + ] 10 -8.7 = 10^(log) [H 3 O + ] [H 3 O + ] = 2.0 x 10 -9 M 1.995…x10 -9 [OH - ] = 1 x 10 -14 [OH - ] = 5.0 x 10 -6 M pH + pOH = 14

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Backwards problem

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  1. Backwards problem • What is the [H3O+] and [OH-] and pOH of a solution with a pH of 8.7? • 8.7 = -log [H3O+] • -8.7 = log [H3O+] • 10-8.7 = 10^(log) [H3O+] • [H3O+] = 2.0 x 10-9 M • 1.995…x10-9 [OH-] = 1 x 10-14 • [OH-] = 5.0 x 10-6 M • pH + pOH = 14 • 8.7 + pOH = 14 • pOH = 5.3

  2. Problem • What is the pH, pOH and [H3O+] of a soln. with a [OH-] conc. of 2.90 x10-4 M? • [H3O+] 2.9 x 10-4 = 1 x 10-14 • [H3O+] = 3.45 x 10-11 M • pH = -log 3.448275 x 10-11 • pH = 10.5 • 10.5 + pOH = 14 • pOH = 3.5

  3. Problem • What is the pH, [OH-] and [H3O+] of a solution with a pOH of 11.1? • 11.1 + pH = 14 • pH = 2.9 • [H3O+] = antilog (-2.9) • [H3O+] =1.3 x10-3 M • [OH-] = 7.9 x10-12 M

  4. Another • What is the pH, pOH, and [OH-] of a solution with a [H3O+] of 4.90x10-8 M? • pH = - log 4.90x10-8 • pH = 7.31 • [OH-] = 2.04 x10-7 M • pOH = 6.69

  5. More • What is the pH, pOH and [H3O+] of a solution with a [OH-] of 1.78x10-12 M? • pH = 2.25 • [H3O+] = 5.62 x10-3 M • pOH = 11.7

  6. Continuing • What is the [OH-] and [H3O+] of a solution with a pH of 9.43? • [H3O+] = antilog (-9.43) • [H3O+] =3.72 x10-10 M • [OH-] = 2.69 x10-5 M • pOH = 4.57

  7. Last one • What is the pH and [OH-] of a solution with a [H3O+] of 2.7x10-6 M? • pH = - log 2.7x10-6 • pH = 5.6 • [OH-] = 3.7 x10-9 M • pOH = 8.4

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