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Acids & Bases Lesson 6 Strong Acid-Base Calculations

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Strong Acids & Bases Calculations

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When we consider strong acids and bases, remember this: They ionize 100% In other words, [strong acid] = [H 3 O + ] [strong base] = [OH - ] When you mix the acid with the base, consider which concentration of H 3 O + or OH - is in excess.

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Strong Acids & Bases Calculations Part I: strong acid or strong base only in water Part II: Mixing the strong acid and the strong base together.

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Part I: strong acid or strong base only in water

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1.Calculate the pH of 0.40 M HI. HI H + +I - 0.40 M0.40 M0.40 M pH = -Log[H + ] pH = -Log[0.40] pH = 0.40

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2.Calculate the pH of 0.030 M Ba(OH) 2. Ba(OH) 2 Ba 2+ +2OH - 0.030 M0.030 M0.060 M pOH = -Log[OH - ] pOH = -Log[0.060] pOH = 1.22 pH + pOH = 14.00 pH + 1.22 = 14.00 pH = 12.78

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Try: Calculate the pH of 0.020 M Mg(OH) 2

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3.Calculate the pH of 100.0 mL of 1.0 M HCl after 300.0 mL of water is added to it. HCl H + +Cl - 1001.0 M 4000.25 M0.25 M pH = -Log[H + ] pH = -Log[0.25] pH=0.60

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Try: Calculate the pH and pOH of 200.0 mL of 2.0 M HCl after 300.0 mL of water is added to it.

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Part II: Mixing solutions of the strong acid and the strong base together. Helpful hints: Start as always by getting your [H 3 O + ] And [OH - ] -Hydronium ion and Hydroxide ion will neutralize each other, however if there is extra of one of the two -Find the excess/extra you have. -If you have extra [OH - ], your solution will be basic. - If you have extra [H 3 O + ], your solution will be acidic.

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Example: 200.0 mL of 0.200 M HCl is mixed with 400.0 mL of 0.250 M NaOH. Calculate the pH of the new solution.

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TRY: calculate the final [H 3 O + ], [OH - ] and new pH in a solution formed when 150.0 mL of 1.5 M HNO 3 is added to 250.0mL of 0.80 M KOH

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example How many moles of HCl (g) must be added to 40.0mL of 0.180 M NaOH to produce a solution having pH= 12.500, if it is assumed that there is no change in volume when the HCl is added?

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TRY: How many moles of HCl (g) must be added to 30.0mL of 0.170 M Ca(OH) 2 to produce a solution having pH= 10.500, if it is assumed that there is no change in volume when the HCl is added?

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Example: calculate the pH resulting from mixing 25.0 mL of 0.0420 M Ba(OH) 2 with 125.0 mL of 0.0120 M HCl.

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TRY: calculate the pOH resulting from mixing 50.0 mL of 0.0185 M Sr(OH) 2 with 35.0 mL of a solution containing 0.130 g of HCl.

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Ex : A chemist has 2.000 L of 0.00120 M KOH soltuion. What mass of HCl(g) would have to be added to the KOH solution to produce a solution having a pH of 10.857? -assume no change in volume occurs.

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Homework: p.143 #58, 59, 62, 63, 64, 66,67.