The Nature of Acids and Bases Arrhenius Definition Bronsted-Lowry Definition HA + B  A - + HB + Conjugate acid-base pair

Equilibrium Expressions Acid dissociation constant is for the equilibrium that exists as an acid spontaneously dissociates. Works the same as the other equilibrium expressions we’ve been writing.

Acid Strength

Types of acids Diprotic Acids- two hydrogen atoms, dissociate with different strengths. Oxyacids- H is attached to an oxygen. Organic Acids- contain a carboxyl group. Hydrohalic Acids- H attached to a halogen.

Write the equilibrium expression for the autoionization of water. Autoionization of Water Water is amphoteric (properties of acid and base) Do Now

The pH Scale pH = -log[H + ] Related by exponents of 10. As [H + ] increases, the pH will decreases. log K w = log [H + ] + log [OH - ] pK w = pH + pOH 14 = pH + pOH The number of S.F. in the concentration value equals the number of decimal places in the pH value.

Try Me Problems!! Calculate the pH or pOH as required for each of the following solutions at 25 o C, and state whether the solution is neutral, acidic, or basic. a) 1.0 x M OH - b) 1.0 x M OH - c) 1.0 M H +

More Try Me! Calcualte pH and pOH for each of the solutions from the problem before.

Even More Try Me! The pH of a sample of human blood was measured to be 7.41 at 25 o C. Calculate the pOH, [H + ], and [OH-] for the sample.

Acid Strength Matters Identify the MAJOR SPECIES present in your sample. Determine if the autoionization of water will impact the concentration of [H+] or not (compare concentrations)

Strong Acid Example Lets pretend I have 1.0 M HCl. major species: H +, Cl -, H 2 O H + from HCl will be 1.0 M H + from H 2 O will be 1.0 x M H + from H 2 O is negligible. We can now base our calculations on the H + values from our major species.

In the Event of a Weak Acid… 1.Write out major species. 2.Determine if H 2 0’s H + are significant. 3.Write K a for dominating species 4.Use an ICE chart

Weak Acid Example Lets pretend I have 1.0 M HF, solve for [H + ] major species: HF, H 2 O HF H + + F - K a = 7.2 x H 2 O H + + OH - K w = 1.0 x Dominating source of H + : HF

ICE it up! HF H+ + F- I C-x +x +x E 1-x x x Plug into Ka expression, BUT DO NOT SOLVE YET

5% rule If x is small, cross out subtracted/added x’s How small? 5% of original concentration. Similarly, percent dissociation/ionization has formula:

Try Me! Calculate the pH of a solution that contains 1.0 M HCN (K a = 6.2 x ) and 5.0 M HNO 2 (K a = 4.0 x ). Also calculate the concentration of cyanide ion (CN - ) in this solution at equilibrium.

Try Me Trickier! Lactic acid (HC 3 H 5 O 3 ) is a waste product that accumulates in muscle tissue during exertion, leading to pain and fatigue. In a 0.10 M aqueous solution, lactic acid is 3.7 % dissociated. Calculate Ka for the acid.

Bases Strong bases have/cause complete ionization, just like acids. KOH and NaOH are the most common group I soluble strong bases Group II hydroxides are insoluble strong bases Not all bases need to have OH - (Brønsted Lowry) H 3 CNH 2(aq) + H 2 O (l) H 3 CNH 3 + (aq) + OH - (aq)

Common Base Structures AmmoniaMethylamineDimethylamine PyridineEthylamineEphedrine

Useful Application Amines can form soluble acid salts Pseudoephedrine + HCl ↔ pseudophedrineHCl

Strong Base Try Me Calculate the pH of a 5.0 x M NaOH solution.

Weak Base Try Me Calculate the pH of a 15 M solution of ammonia (K b = 1.8 x )

Polyprotic Acids Dissociate stepwise For weak acids, K a1 > K a2 > K a3 Sulfuric acid is a freak because it is strong for hydrogen 1 and a weak acid for hydrogen 2. Only impacts normal process if we are using dilute solutions.

Try ME! Concentrated H 2 SO 4 Calculate the pH of a 1.0 M solution of H 2 SO 4.

Try Me 2! Dilute H 2 SO 4 Calculate the pH of 1.0 x M H 2 SO 4

Regular Type Polyprotics Calculate the pH, and the concentration of each ion formed by the complete dissociation of hydrogen in a 5.0 M solution of phosphoric acid.

Once upon a time there was a salt … What is a salt? What power does it have in solution?

Solution is BasicSolution is Acidic salt of a strong acid and a strong base Solution is Neutral salt of a weak acid and a strong base salt of a strong acid and the C.A. of a weak base salt of the C.B. of a weak acid and the C.A. of a weak base salt with a highly charged metal cation varies

Try This On! Calculate the pH of a 0.10 M NH 4 Cl solution, given that K b for NH 3 is 1.8 x 10 -5

Structural Effects Hydrohalic Acids Bond Strength Bond Polarity Oxyacids Number of Oxygen atoms H-F H-Cl H-IH-Br

OXIDES Covalent oxides in water form acids CO 2 + H 2 O  H 2 CO 3 Ionic oxides in water form bases K 2 O + H 2 O  2KOH If X has high EN, the oxide will act as acid If X has low EN, OH stays together and oxide acts as a base.

Lewis Definition Lewis Acids Accepts e - pair Lewis Bases Dontates e - pair