Ch. 20 Acids and Bases

Observable Properties of Acids and Bases

• Sour Taste• Electrolytes when in

aqueous solution• React with metals to

produce Hydrogen gas• React with hydroxide

ions to produce water and salt

• Bitter Taste• Feel “slippery”• React with acids to form

water and Salt

Electrolytes: Conduct electricity through their dissociation into ions

pH Scale

pH = - log [H+]• Measures the concentration of

Hydrogen ions in solution• The lower the pH number, the

higher the amount of Hydrogen ions in solution.

pH + pOH = 14

pH 1 2 3 4 5 6 7 8 9 10 11 12 13 14Acidic BasicAlkali Neutral

Alkaline

pH = - log [H+]

1 x 10-2 M has a pH 2

When written in scientific notation with a coefficient of 1, the absolute value of the exponent is the pH value of the solution.

What is the pH of 1 x 10-5 M solution?

pH = - log [H+]Calculate the pH of a solution that has a hydrogen ion concentration of 4.3 x 10-8 M.

pH = - log [H+]Calculate the pH of a solution that has a hydrogen ion concentration of 4.3 x 10-8 M. pH = - log [H+]pH = - log (4.3 x 10-8)pH = - (log 4.3 + log 10-8)pH = - (0.633) – (-8)pH = 7.367

Your Turn. pH = - log [H+]

Calculate the pH of a solution that has a hydrogen ion concentration of 2.0 x 10-5 M.

pH = 4.7

Calculating pOHpOH = - log [OH-]

Plug and chug using the same order of operations as the pH problem solving!

** You may be asked to solve for pH when given a hydroxide ion concentrationRemember that pH + pOH = 14How would you go about solving this problem?

Measuring pH• Acid Base Indicators– Color Change:

Red = acidic Blue = basic

Measuring pH

• pH Meters or pH Probes

Acids:

• Hydrogen Ion donating

Bases:

• Hydrogen ion accepting

NH3 (aq) + H2O(l) NH4+ (aq) + OH-(aq)

Strong Acids and Bases

Fully dissociate in solution to their ionic forms

HCl H+ + Cl-

Weak Acids and Bases: Partially dissociate

pH Titration Curves

Time to Practice!!!