Do Now – May Day! 1.How do you feel about the quiz you just took (or will make-up today?) 2.Write anything that you know about acids and bases?

Agenda Do Now/Announcements Solutions, Solvation, Ionization Introduction to Acids and Bases Exit Ticket

Objectives SWBAT describe the ionization of acids and bases using equations. SWBAT describe acids and bases using the Arrhenius and Bronsted-Lowry models.

First! We have to understand a little more about solutions A solution is a uniform mixture that may contain solids, liquids, or gases; also known as a homogeneous mixture

Solutions have 2 parts… 1.A solute is a substance dissolved in a solution 2.A solvent a substance that dissolves a solute to form a solution

Remember aqueous solutions? An aqueous solution is a solution in which the solvent is water So are these aqueous solutions? YES!

A little more about aqueous solutions Some solutes exist as aqueous solutions –Examples: sucrose (table sugar) and ethanol (grain alcohol) Other solutes are compounds that form ions when they dissolve in water What is an ion? A CHARGED ATOM OR GROUP OF ATOMS!

When a compound dissolves in water… It undergoes a process called solvation Solvation is the process of surrounding solute particles with solvent particles to form a solution Compounds break down into their ions!

What about table salt? NaCl (aq)  Na + (aq) + Cl - (aq) This (aq) tells us that the salt is dissolved in water!

Some More Examples HCl(g)  H + (aq) + Cl - (aq) NaOH(aq)  Na + (aq) + OH - (aq)

So how does this relate to…..

Well, acids and bases break into ions! Understanding this ionization idea is very important to understanding acids and bases WHY DO WE NEED TO KNOW ABOUT ACIDS AND BASES?

Without acids… You could NOT digest food! Cold drinks would not be the same! Without bases… You could not get your body…or house…or car clean! You could not cure an upset stomach!

The downside of some acids… Acid rain destroys buildings and statues Acid in drinks damages tooth enamel Heart burn hurts! The downside of bases… You find me some! ;O)

PROPERTIES OF…..

Corrosive (‘burns’ your skin) Sour taste (ex: lemons, vinegar) Contains hydrogen ions (H + ) when dissolved in water Has a pH less than 7 Turns blue litmus paper red Reacts with bases to form salt and water Reacts with metals to form hydrogen gas Reacts with carbonates to form carbon dioxide, water, and a salt

Examples Hydrochloric acid (HCl) (stomach juice) Sulphuric acid (H2SO4) Nitric acid (HNO3) Carbonic acid (H2CO3) (cold drinks) Uric acid (C5H4N4O3) (urine) Ascorbic acid/Vitamin C (C 6 H 8 O 6 ) (fruit) Acetic acid (HC2H 3 O 2 ) (vinegar) Tannic acid (C76H52O46) (tea and wine)

ACID REACTIONS Acids react with metals to form hydrogen gas Zn(s) + HCl(aq)  ZnCl 2 (aq) + H 2 (g) Acids also react with hydrogen carbonates to form carbon dioxide gas (water and a salt) NaHCO3(s) + HC2H 3 O 2 (aq)  NaC2H 3 O 2 (aq) + H2O(l) + CO 2 (g)

ACID REACTIONS PRACTICE 1.Acids react with metals to form hydrogen gas Write a balanced equation for the reaction that occurs between magnesium metal and nitric acid 2. Acids also react with hydrogen carbonates to form carbon dioxide gas Write a balanced equation for the reaction that occurs between calcium carbonate and hydrobromic acid

Soapy/slippery feel Bitter taste Has a pH more than 7 Turns red litmus paper blue Many alkalis (soluble bases) contain hydroxide ions (OH-) Reacts with acids to form salt and water

Sodium hydroxide (NaOH) (caustic soda) Calcium hydroxide (Ca(OH)2) (limewater) Ammonium hydroxide (NH4OH) (ammonia water) Magnesium hydroxide (Mg(OH)2) (milk of magnesia) Many bleaches, soaps, toothpastes and cleaning agents EXAMPLES

Why are some aqueous solutions acidic, others basic, and others neutral? Scientists have found out that all water (aqueous) solutions contain hydrogen ions (H + ) and hydroxide ions (OH - ) The relative amounts of the two ions in a solution determine whether a solution is acidic, basic, or neutral (not acidic or basic)

The Trinity of Solutions An acidic solution contains more hydrogen ions (H + ) than hydroxide ions (OH - ) A basic solution contains more hydroxide ions (OH - ) than hydrogen ions (H + ) A neutral solution contains an equal amount of hydrogen ions and hydroxide ions

Water, oh water…. Water is the usual solvent for acids and bases It produces an equal number of hydrogen ions and hydroxide ions in a process called self-ionization H 2 O(l) + H 2 O(l) H 3 O + (aq) + OH - (aq) hydronium ion hydroxide ion

Hydronium Ion is Hydrogen Ion H 2 O(l) + H 2 O(l) H 3 O + (aq) + OH - (aq) H 2 O(l)H + (aq) + OH - (aq)

Arrhenius Model for Acids and Bases An Arrhenius acid is a substance that contains hydrogen and ionizes to produce hydrogen ions in aqueous solution HCl  H + + Cl - A Arrhenius base is a substance that contains hydroxide group and ionizes to produce hydroxide ions in aqueous solution NaOH  Na + + OH - This is called DISSOCIATION!

Historical views on acids The more recent Bronsted-Lowry concept is that acids are H + (proton) donors and bases are proton acceptors Ionization + ClH H H O + H H HO + O (e.g. H 2 SO 4 ) was originally thought to cause acidic properties. Later, H was implicated, but it was still not clear why CH 4 was neutral. Arrhenius made the revolutionary suggestion that some solutions contain ions & that acids produce H 3 O + (hydronium) ions in solution.

Bronsted-Lowry Model for Acids and Bases A Bronsted-Lowry acid is a hydrogen-ion donor A Bronsted-Lowry base is a hydrogen-ion acceptor

Bronsted-Lowry Model for Acids and Bases A Bronsted-Lowry acid is a hydrogen-ion donor. A Bronsted-Lowry base is a hydrogen-ion acceptor HX(aq) + H 2 O(l)  H 3 O + (aq) + X - (aq) ACID BASE CONJUGATE ACID CONJUGATE BASE

The Bronsted-Lowry concept In this idea, the ionization of an acid by water is just one example of an acid-base reaction. Acids and bases are identified based on whether they donate or accept H +. “Conjugate” acids and bases are found on the products side of the equation. A conjugate base is the same as the starting acid minus H +. + ClH H H O + H H HO + acidbase conjugate acidconjugate base conjugate acid-base pairs

Conjugate Acids and Bases HX(aq) + H 2 O(l)  H 3 O + (aq) + X - (aq) A conjugate acid is the species produced when a base accepts a hydrogen ion from an acid A conjugate base is the species produced when an acid acid donates a hydrogen ion to a base ACID BASE CONJUGATE ACID CONJUGATE BASE

Practice problems Identify the acid, base, conjugate acid, conjugate base, and conjugate acid-base pairs: acidbase conjugate acidconjugate base HC 2 H 3 O 2 (aq) + H 2 O (l)  C 2 H 3 O 2 – (aq) + H 3 O + (aq) conjugate acid-base pairs acidbase conjugate acidconjugate base OH – (aq) + HCO 3 – (aq)  CO 3 2– (aq) + H 2 O (l) conjugate acid-base pairs

A Bronsted-Lowry Example HF + H 2 O  H 3 O + + F - ACID BASE CONJUGATE ACID CONJUGATE BASE

A Bronsted-Lowry Example NH 3 + H 2 O  NH OH - ACID BASE CONJUGATE ACID CONJUGATE BASE

Water, oh water… HF + H 2 O  H 3 O + + F - NH 3 + H 2 O  NH OH - Water can act as both an acid and a base; therefore, it is considered an amphoteric substance H2OH2O H2OH2O

Bronsted-Lowry Practice Identify the Conjugate Acid-Base Pairs in the reactions on page 599

Practice Time! Answer the following questions on page 630 in your book: 40-46, 48-51

Exit Ticket 1.What is an Arrhenius acid? 2.What is a Bronsted-Lowry base? 3.Is HBr an acid or a base? How do you know?