Question 1: Name the acid HBr Question 2:Name the acid H 3 PO 4 Academic Chemistry March 21,2012

Section 20.3 – Other definitions of Acids and Bases Arrhenius Acids and Bases:  Acid: Hydrogen containing compound that ionize to yield a hydrogen ion in solution.  Base: Compounds that ionize to yield a hydroxide ion in solution.

Brønsted – Lowry Acids and Bases They felt the Arrhenius definition was too limiting.  Acids: Hydrogen ion donor  Bases: Hydrogen ion acceptor

Brønsted – Lowry Acids and Bases  Examples: NH 3 + H 2 O ↔ NH OH -  H 2 O donated the H + - Acid  NH3 accepted the H + - Base HCl + H 2 O ↔ H 3 O + + Cl -  HCl donated the H + - Acid  H 2 O accepted the H + - Base

Conjugate Acids:  Particle formed when a base gains a hydrogen ion. Ex: NH 3 + H 2 O ↔ NH OH - B A CA CB Conjugate Base:  Particle that remains when an acid has donated a hydrogen ion. Ex: HCl + H 2 O ↔ H 3 O + + Cl - A B CA CB Amphoteric:  Substance that can act as both an acid or a base.

Strong Acids and Bases Strong Acids/Bases:  Those that ionize completely in solution. Ex: HCl, NaOH Weak Acids/Bases:  Those that only slightly ionize in solution. Ex: NH 3, Acetic Acid (vinegar) Tooth decay is caused by the weak acid – lactic acid: C 3 H 6 O 3

Section 21.1 Neutralization Reactions occur when… Acid + Base ↔ Water + “Salt”  Salt: Anion from acid and the cation from the base join together to form a salt. Where do we see this process?  Antacids  Farmers controlling the pH of soil  Formation of caves

Section 21.1 A strong acid + a strong base = neutral solution Examples:  HCl + NaOH ↔ H 2 O + NaCl  HCl + KOH ↔ H 2 O + KCl  How many moles of HCl are needed to neutralize 6 mols of KOH? 1 st ask, what is the mol ratio and then set it up as a proportion.

Neutralization Reactions So far, everything we’ve talked about is a 1mol ratio – 1 mol acid : 1 mol base Sometimes, this reaction is not 1:1 H 2 SO 4 + 2NaOH ↔ Na 2 SO 4 + 2H 2 O  One mol of sulfuric acid is needed to neutralize 2 mols of NaOH.  How many mols of NaOH are needed to neutralize 4 mols of H 2 SO 4 ?

Question 1: If the pH is 2.3 what is the pOH? Question 2: what is the pH for a neutral substance Academic Chemistry March 23,2012

Titrations  Titration: The process of adding a known amount of solution of known concentration to determine the concentration of the other solution.  If you don’t know the concentration of one solution, you can figure it out by performing a neutralization reaction, or titration, with a standard solution.  A standard solution is one of known concentration.

Performing Titrations Steps in a neutralization reaction:  1. A measured volume of an acid solution of unknown concentration is added to a flask.  2. Several drops of indicator are added to the solution.  3. Measured volumes of a base with a known concentration are mixed into the acid until it barely changes color.

Performing Titrations, cont. End Point: The point at which the indicator changes color.  Once you have reached the end point, you can perform calculations to find the unknown solution. Let’s show a video!

Performing Titrations, cont. Example: A 25 mL solution of H 2 SO 4 is completely neutralized by 18 mL of 1.0 M NaOH. What is the concentration of H 2 SO 4 solution?  Step 1: Balanced equation ____H 2 SO 4 + ____NaOH ↔ ____Na 2 SO 4 + ____H 2 O  Step 2: Use formula to solve for unknown. M a V a = M b V b A B  A = Number of moles of your Acid  B = Number of moles of your Base  M = Molarity  V = Volume (in Liters)