# TOPIC: pH 1. NaCl 2. C 2 H 5 OH 3. H 2 SO 4 4. NaOH 5. C 12 H 22 O 11 6. CaI 2 7. HF 8. Mg(OH) 2 9. NH 3 10.CH 3 COOH Do Now: Identify as acid, base, salt,

## Presentation on theme: "TOPIC: pH 1. NaCl 2. C 2 H 5 OH 3. H 2 SO 4 4. NaOH 5. C 12 H 22 O 11 6. CaI 2 7. HF 8. Mg(OH) 2 9. NH 3 10.CH 3 COOH Do Now: Identify as acid, base, salt,"— Presentation transcript:

TOPIC: pH 1. NaCl 2. C 2 H 5 OH 3. H 2 SO 4 4. NaOH 5. C 12 H 22 O 11 6. CaI 2 7. HF 8. Mg(OH) 2 9. NH 3 10.CH 3 COOH Do Now: Identify as acid, base, salt, or covalent Electrolyte or Not 1. SALT - ELECTROLYTE 2. COVALENT -NO 3. ACID- ELECTROLYTE 10. ACID- WEAK ELECTROLYTE 9. BASE- WEAK ELECTROLYTE 8. BASE- ELECTROLYTE 7. ACID- WEAK ELECTROLYTE 6. SALT - ELECTROLYTE 5. COVALENT -NO 4. BASE- ELECTROLYTE

Acid, Base, or Neutral Neutral solution: [H +1 ] = [OH -1 ] Neutral solution: [H +1 ] = [OH -1 ] Acidic solution: H +1 > OH -1 pH= LESS THEN 7 Acidic solution: H +1 > OH -1 pH= LESS THEN 7 Basic solution: OH -1 > H +1 pH= GREATER THEN 7 Basic solution: OH -1 > H +1 pH= GREATER THEN 7

pH scale measure how acidic/basic a substance is. Ranges from 0-14 0  more acidic more basic  14 more alkaline (another word for basic) Logarithmic scale (based on powers of 10) each decrease of one unit of pH represents a 10x increase in H + concentration E: pH 4 is ten times more acidic then pH 5 Ex: pH 10 is ten times more basic then pH 9

Calculating pH pH=-log [H + ] – [H + ] = concentration – Ex. 0.01M HCl has a pH of? pH = -log(0.01) pH=2

Concentration from pH Which is more concentrated a HCl solution with a pH or 2 or 3? – pH 2 is 10 times more concentrated (remember changes by 10) – Try it Antilog (2 nd log) 2 = 0.01M Antilog 3 = 0.001M

Try to remember: The lower the pH – the high the concentration of H+ ions

So how do you find pH of a base? All you have are OH - ions – ONLY CAN CALC pOH pOH=-log [OH - ] – [OH - ] = concentration – pH + pOH = 14 – So 14 – pOH = pH – Ex. 0.01M NaOH has a pH of? pOH = -log(0.01) pOH=2 pH = 14-2 = 12

pH range 0 to 14 – with 7 being neutral pH = 0, strongly acidic pH = 14, strongly basic

Because it’s based on powers of 10 there is a trick If molarity of acid is.001M =10 -3 pH = 3 If molarity of acid is.00001M = 10 -5 pH = 5 If molarity of base is.001M = 10 -3 pOH = 3 pH 14-3 = 11 If molarity of base is.00001M = 10 -5 pOH = 5 pH 14-5 = 9

If pH = 4 If pH = 4 [H +1 ] = ? pOH = ? [OH -1 ] = ? pH + pOH = 14 4 + X = 14 X =10 Antilog(-pH) = [H +1 ] Antilog(-4) = 1 x 10 -4 M Antilog(-10) = [OH -1 ] 1x10 -10 M = [OH -1 ]

If the [OH -1 ] = 1 X 10 -3 M pOH = ? pH = ? [H +1 ] = ? pOH = -log[OH -1 ] = -log(10 -3 ) = 3 pH + pOH = 14 X + 3 = 14 X = 11 Antilog(-11) = 1x10 -11 M

[H +1 ] = 1 x 10 -5 M I f the [H +1 ] = 1 x 10 -5 M The pH = ? The pOH = ? The [OH - ] = ? pH=-Log (10 -5 ) =5 pH + pOH =14 5+x =14 X=9 Antilog(-9) = 1x10 -9 M

How to safely test pH Instruments – use a pH meter Indicators – use a series of indicators See if the substance reacts with a metal other than Cu, Ag, or Au NEVER “ taste ”

Indicator substance that changes color over narrow pH range substance that changes color over narrow pH range Use several indicators to narrow down pH range of substance Use several indicators to narrow down pH range of substance

Practice using table M 1. What indicator is yellow with a pH 9.8 2. Which indictor is blue with a pH of 5.6 0-3.0 4.5-14 3.1.-4.4 Orange Green Pink Purple Green 0-3.7 5.5-14 3.8-5.4 7.7-14 8.4-14 9.7-14

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