PROPERTIES OF ACIDS AND BASES

Acids taste sour or tart (vinegar, lemons) aqueous solutions of acids are electrolytes cause indicators to change colors many metals react with acids to produce H 2 gas react with hydroxides to form a salt and water most formulas begin with H. pH 7 [H 3 O+] > 1.0 x 10 -7, [OH - ] < 1.0 x produce H 3 O + (aka H + ) ions in water solutions

Common uses of acids HNO 3 or HCl are used for etching metals. HF is used for etching glass.

Bases bitter taste (soap, unsweetened chocolate) bases are electrolytes in aqueous solution cause indicators to change colors feel slippery react with acids to form a salt and water often contain OH -, or ammonia NH 3 pH > 7, pOH < 7 [H 3 O + ] 1.0 x produce OH - ions in water solutions

hydroxide ion (OH - ) –formed when a water molecule loses a H + hydronium ion (H 3 O + ) –formed when a water molecule gains a H + H 2 O + H +  H 3 O + *your text uses H + and H 3 O + interchangeably*

Acidic solutions [H 3 O + ] > [OH - ] [H 3 O + ] > 1.0 x Basic solutions [OH - ] > [H 3 O + ] [OH - ] > 1.0 x [H 3 O + ] < 1.0 x 10 -7

Acidic or Basic? [H 3 O + ] = 1 x [H 3 O + ] = 1 x [OH - ] = 1 x [OH - ] = 1 x H + > 1.0 x H + < 1.0 x OH - > 1.0 x OH - < 1.0 x Acidic Basic Basic Acidic [H 3 O + ] = 1 x [H 3 O + ] = 1 x 10 -1

pH Concept: pH = - log [H 3 O + ] or - log [H + ] A logarithm (log) is the exponent to which 10 must be raised to get the number. log base value = exponent If X = 10 Y, then log 10 X = Y In calculator enter: - log (value)

Example: log 10 1 = 1 log = -5 If [H 3 O + ] = 1.0 x pH = - log [H 3 O + ] then pH = -log [1.0 x ] = 4.00

pH problems: What is the pH if: [H 3 O + ] = 1 x pH = __________ pH = - log [H 3 O + ] [H 3 O + ] = 1 x pH = __________ pH = - log [H 3 O + ] pH > 7 is basic pH < 7 is acidic pH = 7 is neutral 5 13 Acidic Basic

pOH = -log [OH - ] What is the pOH if: [OH - ] = 1 x pOH = pOH = -log [OH - ] [OH - ] = 1 x pOH = pOH = -log [OH - ] 4 3 Basic

pH + pOH = 14 pH = 6pOH = pH = 4pOH = pOH = 3pH = pOH = 11pH =

[H 3 O + ] = antilog (-pH) [OH - ] = antilog (-pOH) pH = 7.00so[H 3 O + ] = [H 3 O + ] = antilog (-7.00) pH = 3.00[H 3 O + ] = [H 3 O + ] = antilog (-3.00) pOH = 8.00[OH - ] = [H 3 O + ] = [OH - ] = antilog (-8.00) 14 = 8 + xx = 6 Calculator: 10 x (-pH.) 1.0 x x x x 10 -7

Using a programmable calculator for pH: What is the pH if [H 3 O + ] = 5.2 x pH = - log (H 3 O + ) pH = (-) log (5.2 x ) - log 10 (5.2 x10 -2 ) enter pH = 1.3

Using a programmable calculator for antilogs: What is the [H 3 O + ] if the pH is 4.92? [H 3 O + ] = antilog (-pH) [H 3 O + ] = antilog (-4.92) Calculator: 10 x (- 4.92) Enter [H 3 O + ] = 10 x is the 2nd function of the log key 1.2 x 10 -5

Example: pH = 9.29 [H 3 O + ] = ? [H 3 O + ] = antilog (-pH) [H 3 O + ] = antilog (-9.29) Calculator: 10 x (-9.29) Enter [H 3 O + ] = 5.13 x

Indicators Indicators are substances that change color in solutions of different pH. Indicators are usually weak acids. They are one color in their acid form and a different color in their base form. HIn  H + + In - Help determine approximate pH

Indicators cont. phenolphthalein colorless in acid pink in base changes at pH

Indicators cont. litmus blue litmus turns red in acid red turns blue in base universal indicator mixture of indicators changes into different colors at each pH (rainbow colors)

Indicators cont. bromothymol blue blue in basic solutions yellow in acidic solutions green in neutral solutions

Common acids Common bases HClNaOH HNO 3 KOH H 2 SO 4 Ca(OH) 2 H 3 PO 4 Mg(OH) 2 HC 2 H 3 O 2 NH 3 H 2 CO 3

Acid-Base Reactions When acids and bases react, the products most commonly formed are water and a salt (ionic compound). This is called a neutralization reaction.