ACIDS AND BASESa review

Arrhenius Acids and Bases• Acids = H+, Bases = OH-

Modified• Acids = H3O+, Bases = OH-

Modified Arrhenius

• Uses the idea that the substance will react with water to form H3O+ instead of just H+

Formulas You NEED to Remember

Example

• What is the [OH-] in a solution with [H3O+] = 2.59x10-4 mol/L?

Example 2

• If 2.50g of NaOH were dissolved in water to produce 500mL of solution, what would be [H3O+] and [OH-], pH and pOH?

Example 3

• A solution has pH = 5.75. What are the values of pOH, [H3O+] and [OH-]?

• pOH = 8.25

• [H3O+] = 1.8 x 10-6 M

• [OH-] = 5.6 x 10-9 M

NeutralizationsAcid + Base = Water + salt

Modified• hydronium + hydroxide = water

Strong Acids• completely give up their H+ in

solution (reacts completely to form H3O+)• very low pH • high conductivity• fast reaction rate

Weak Acids• partially react with water to

form H3O+• medium to low pH• low conductivity• slow reaction rate

Strong Bases• completely dissociate to

form OH- in water• very high pH• high conductivity• fast reaction rate

Weak Bases• partially dissociates to OH-• medium to high pH• low conductivity (molecular)• slow reaction rate

Measuring pH• pH can be

measured precisely using a pH meter• or you could

use an indicator

Example

• Separate samples of a solution of unknown pH cause the following acid base indicator colours

• Orange IV = yellow• Bromothymol blue = blue• Phenolphthalein = colourless• What is the solution pH?

• Hint: use the indicator chart at the back of your workbook!

Polyprotic Substances

• contain more than one hydrogen (or hydroxide) in their compound formulas• HxA or A(OH)x

• polyprotics react multiple times with water• i.e. H3PO4 + H2O• in general, polyprotic acids (bases)

are weak acids (bases) whose reaction with water decreases with each successive step