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pH and pOH

pH and pOH. Measuring acidity and basicity. pH. The pH scale is used to measure the acidity of a solution. pH is a measure of the concentration of hydronium ions, [H 3 O + ], in a solution. The scale ranges from 0 - 14 A pH value of 7 indicates neutrality.

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pH and pOH

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  1. pH and pOH Measuring acidity and basicity.

  2. pH • The pH scale is used to measure the acidity of a solution. • pH is a measure of the concentration of hydronium ions, [H3O+], in a solution. • The scale ranges from 0 - 14 • A pH value of 7indicates neutrality. • A pH value of 0indicates the strongest acid. • A pH value of 14 indicates the weakest acid.

  3. pH

  4. Calculations Involving pH pH = -log [H3O+] • Concentration of hydronium ions is usually expressed in scientific notation form. • Coefficient must be greater than or equal to 1 and less than 10. • Exponent is a number between -14 and 0.

  5. Interpreting pH Values • When coefficient equals one, the pH is equal to the exponent (without negative sign). • Once the pH is determined: • pH less than 7 means acidic • pH of exactly 7 means neutral • pH more than 7 means basic

  6. pH Problems • What is the pH of a solution if the concentration of hydronium ions is 1 x 10-3? • Use exponent to determine pH: • pH = 3 • Is this solution acidic, neutral, or basic? • pH is less than 7: • Solution is acidic.

  7. pH Problems • If the pH of a solution is 10, what is the concentration of hydronium ions? • Convert the pH to the exponent in scientific notation form: • Concentration of hydronium ions = 1 x 10-10 • Is this solution acidic, neutral, or basic? • pH is more than 7: • Solution is basic.

  8. pOH • The pOHscale is used to measure the basicity of a solution. • pOHis a measure of the concentration of hydroxide ions, [OH-], in a solution. • The scale ranges from 0 - 14 • A pOHvalue of 7indicates neutrality. • A pOHvalue of 0indicates the strongest base. • A pOHvalue of 14 indicates the weakest base.

  9. Calculations Involving pOH pOH= -log [OH-] • When coefficient equals one, the pOHis equal to the exponent (without negative sign). • Once the pOHis determined: • pOHless than 7 means basic • pOH of exactly 7 means neutral • pOH more than 7 means acidic

  10. pOH Problems • What is the pOHof a solution if the concentration of hydroxide ions is 1 x 10-8? • Use exponent to determine pOH: • pOH = 8 • Is this solution acidic, neutral, or basic? • pOH is more than 7: • Solution is acidic.

  11. pOH Problems • If the pOHof a solution is 7, what is the concentration of hydroxide ions? • Convert the pOH to the exponent in scientific notation form: • Concentration of hydroxide ions = 1 x 10-7 • Is this solution acidic, neutral, or basic? • pOH is exactly 7: • Solution is neutral.

  12. pH and pOH of Pure Water [H3O+]= (1 x 10-7) & [OH-] = (1 x 10-7) • What is the pH of pure water? • 7 • What is the pOH of pure water? • 7 • What is the sum of the pH and pOH of pure water? • 14

  13. Relationship Between pH & pOH • pH + pOH = 14 • pH = 14 - pOH • pOH = 14 - pH Most Basic Most Acidic

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