 # Ch. 20 Acids and Bases. Observable Properties of Acids and Bases Sour Taste Electrolytes when in aqueous solution React with metals to produce Hydrogen.

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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 14 Acidic Basic AlkaliNeutral 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 pOH pOH = - 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 concentration Remember that pH + pOH = 14 How 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 NH 3 (aq) + H 2 O (l)  NH 4 + (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!!!

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