Stay Strong or Be Neutral ACIDS & BASES Stay Strong or Be Neutral

Acids and Bases Arrhenius Model (1884) Bronsted-Lowery Model (1923) Acid produces excess H+ in water Base produces excess OH- Very practical, but one disadvantage. It restricts the number of reactions that can be considered acid/base Bronsted-Lowery Model (1923) Acid is H+ donor Base is H+ acceptor

Strong Acids and Bases Strong Acids Strong Bases HCl (aq) HBr (aq) HI (aq) HNO3 (aq) HClO4 (aq) H2SO4 (aq) Strong Bases LiOH NaOH KOH Ca(OH)2 Sr(OH)2 Ba(OH)2

Strong: Ionize 100% pH = -log[H3O+ ] Strong acid HA +H2O H3O+ + A- [Acid] = [H3O+ ] pH = -log[H3O+ ] Base must be soluble hydroxide BOH  B+ + OH- [Base] = [OH-] pOH = -log [OH-]

Weak: Don’t ionize 100% Bronsted-Lowry model for Acid-Base Reactions HA + H2O D H3O+ + A- HA acid and A- conjugate base B + H2O D BH+ + OH- B base and BH+ conjugate acid

Conjugate Acid/Base Conjugate Acid Conjugate Base HF F- HSO4- SO42- NH4+ NH3

In this unit we are only going to be dealing with STRONG ACIDS/BASES.

Determining Acid or Base We determine if a substance is an acid or base based on its pH. In lab we use… pH meter Indicators Phenolphthalein pH of 9 Methyl Red pH of 5 Bromthymol blue pH of 7 pH strips

Review pH pH less than 7 is acidic pH equal to 7 is neutral pH greater than 7 is basic Remember pH is based on a power of 10 The smaller the pH the stronger the acid The larger the pH the stronger the base

The Ion product of water Because of the water decomposes, it has a Kw constant of 1.0 E-14 Kw stands for equilibrium of water constant

Formulas pH + pOH= 14 pH = -log[H+] pOH = -log[OH-] [H+] * [OH-] = 1 x 10-14

Find the pH and pOH with the following [H+] 1.0 M 1.7 E-4 M 6.8 E-8 M

Calculate the [H+] and [OH-] in solutions with the following pH. 4.0 8.52 0.00 12.60

Solution X has pH 11. 7. Solution Y has [OH-]= 4. 5 E-2 Solution X has pH 11.7. Solution Y has [OH-]= 4.5 E-2. Which solution is more basic? Which has a higher pH?

Milk of magnesia has a pH of 10. 5 Milk of magnesia has a pH of 10.5. Calculate the concentration of the hydrogen ion. Calculate the ratio of the hydrogen ions concentration of gastric juice, pH 1.5, to that of milk of magnesia.

Homework 1: Page 374 (7-15 odd)

We can also find the pH of a solution based on the [H+] and [OH-] Find the [H+] and pH of the following solutions. 1.75 L of a 37.5% (by mass) solution (d=1.0g/mL) of HCL. What is the pH of 0.175 L of the same solution? A solution made up of 22g of HBr dissolved in enough water to make 479 mL of solution. What is the pH if the same mass of HBr is dissolved in enough water to make 47.9 mL of solution?

Find pH What is the pH of a solution obtained by adding 145 mL of 0.575 M HCl to 493 mL of a HNO3 solution with a pH of 1.39. Assume the volumes are additive.

Find [OH-], [H+], pH & pOH 45.0 mL of 0.0921 M Ba(OH)2 diluted with enough water to make 350 mL of solution. A solution made by dissolving 4.68 g of NaOH in enough water to make 635 mL of solution.

Homework 2: 374 17-23 odd

Acid/Base Titrations Strong acids/bases ionize completely in water. The neutralization reactions that takes place when any strong acid reacts with any strong base can be represented by a net ionic equation. **Write the equations on the board.

Acid/Base Titrations The K of the formation of water through acid/base neutralization is 1.0 E14. Such an enormous K value means that for all practical purposes this reaction geos to completion. Titrations are based on stoichiometric factors At the equivalence point, the pH is 7 Near the equivalence point, the pH varies greatly.

Acid/Base titrations When 50.00 mL of 1.0 M HCl is titrated with 1.0 M of NaOH, the pH increases. Find the initial pH Find the pH after 49.99 mL NaOH has been added. Find the pH after 50.01 mL of NaOH has been added. Find out how much NaOH is needed to reach the equivalence point. Based on the pH’s found above, what indicators can be used to in this acid base reaction. Find the pH ½ way to the equivalence point. Find the pH 5 mL past the equivalence point.

Homework 3: page 398 43 & 44