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pH (hydrogen power) Scale

pH (hydrogen power) Scale. Negative of the common logarithm of the hydronium ion concentration. pH = -log[H 3 O+] pH is used because the conc. Quantities are small.

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pH (hydrogen power) Scale

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  1. pH (hydrogen power) Scale • Negative of the common logarithm of the hydronium ion concentration. pH = -log[H3O+] pH is used because the conc. Quantities are small. Logarithm of a number is the power to which 10 must be raised to equal the number. A neutral solution at 25°C has [H3O+] of 1x10-7 M. The logarithm of 1x10-7 is -7.0. The pH is determined as follows. pH = -log[H3O+] = -log(1x10-7) = -(-7.0) = 7.0

  2. pOH pOH = -log[OH-] A neutral solution at 25C has a [OH-] of 1x10-7 M. Therefore, the pOH is 7.0. pH + pOH = 14.0 The negative log of Kw at 25°C, 1x10-14 is 14.0.

  3. What is the PH of a 1.0x10-3 M NaOH solution? [H3O+][OH-] = 1.0x10-14 [H3O+] = 1.0x10-14 = 1.0x10-14 = 1.0 x10-11M [OH-] 1.0x10-3 pH = -log[H3O+] = -log(1.0x10-11) = 11.00 basic

  4. Determine the hydronium ion concentration of an aqueous solution that has a pH of 4.0. pH = -log[H3O+] log[H3O+] = -pH [H3O+] = antilog(-pH) 2nd log = 10x [H3O+] = 1x10-4M

  5. Titration • Controlled addition and measurement of the amount of a solution of known concentration required to react completely with a measured amount of a solution of unknown concentration.

  6. Equivalence point – the point at which the two solutions used in a titration are present in chemically equivalent amounts. • Indicators are used to determine the equivalence point (in exp. The pink color). • End point – the point in a titration at which an indicator changes color.

  7. Standard solution – the solution that contains the precisely known concentration of a solute. • Primary standard – highly purified solid compound used to check concentration of the known solution in a titration.

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