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PROPERTIES OF ACIDS AND BASES
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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 10 -7 produce H 3 O + (aka H + ) ions in water solutions
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Common uses of acids HNO 3 or HCl are used for etching metals. HF is used for etching glass.
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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 10 -7 produce OH - ions in water solutions
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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*
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Acidic solutions [H 3 O + ] > [OH - ] [H 3 O + ] > 1.0 x 10 -7 Basic solutions [OH - ] > [H 3 O + ] [OH - ] > 1.0 x 10 -7 [H 3 O + ] < 1.0 x 10 -7
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Acidic or Basic? [H 3 O + ] = 1 x 10 -3 [H 3 O + ] = 1 x 10 -11 [OH - ] = 1 x 10 -4 [OH - ] = 1 x 10 -13 H + > 1.0 x 10 -7 H + < 1.0 x 10 -7 OH - > 1.0 x 10 -7 OH - < 1.0 x 10 -7 Acidic Basic Basic Acidic [H 3 O + ] = 1 x 10 -10 [H 3 O + ] = 1 x 10 -1
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pH Concept: pH = - log [H 3 O + ] or - log [H + ] In calculator enter: - log (value)
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Example: If [H 3 O + ] = 1.0 x 10 -4 pH = - log [H 3 O + ] then pH = -log [1.0 x 10 -4 ] = 4.00
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pH problems: What is the pH if: [H 3 O + ] = 1 x 10 -5 pH = __________ pH = - log [H 3 O + ] [H 3 O + ] = 1 x 10 -13 pH = __________ pH = - log [H 3 O + ] pH > 7 is basic pH < 7 is acidic pH = 7 is neutral 5 13 Acidic Basic
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pOH = -log [OH - ] What is the pOH if: [OH - ] = 1 x 10 -4 pOH = pOH = -log [OH - ] [OH - ] = 1 x 10 -3 pOH = pOH = -log [OH - ] 4 3 Basic
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pH + pOH = 14 pH = 6pOH = pH = 4pOH = pOH = 3pH = pOH = 11pH = 8 10 11 3
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[H 3 O + ] = antilog (-pH) [OH - ] = antilog (-pOH) pH = 7.00so[H 3 O + ] = [H 3 O + ] = 10 -7.00 pH = 3.00[H 3 O + ] = [H 3 O + ] = 10 -3.00 pOH = 8.00[OH - ] = [H 3 O + ] = [OH - ] = 10 -8.00 14 = 8 + xx = 6 [H 3 O + ] = 10 -pH [OH - ] = 10 -pOH 1.00 x 10 -3 1.00 x 10 -8 1.00 x 10 -6 1.00 x 10 -7
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Using a programmable calculator for pH: What is the pH if [H 3 O + ] = 5.2 x 10 -2 pH = - log (H 3 O + ) pH = (-) log (5.2 x 10 -2 ) - log 10 (5.2 x10 -2 ) enter pH = 1.3
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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 1.20 x 10 -5
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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 10 -10
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ACIDS & BASES WORKSHEET IS DUE
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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
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Indicators cont. phenolphthalein colorless in acid pink in base changes at pH 8.0 -10.0
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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)
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Indicators cont. bromothymol blue blue in basic solutions yellow in acidic solutions green in neutral solutions
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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
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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.
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