Acids & Bases Lesson 6 Strong Acid-Base Calculations

Strong Acids & Bases Calculations

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.

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.

Part I: strong acid or strong base only in water

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

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

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

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

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

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.

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

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

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

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

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

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

Ex : A chemist has L of 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 ? -assume no change in volume occurs.

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