Acids and Bases http://flowerpower89.files.wordpress.com/2010/10/hippies.jpg http://michaelweishan.com/gardenblog/?p=2103

Review -What is an ion? -What are the properties of an acid? -What are some common acids? -What are the properties of a base? -What are some common bases? -What does pH mean?

Acids -From latin word "acere" which means sour -Sourness is the taste that detects acidity -Many sour candies use citric acid

Bases -Another older word we use for some basic is alkali -The word is derived from Arabic al qalīy -meaning roasting which had to do with a process from making soap with lime -It was known that they caused burns on skin when concentrated -These substances also felt slippery

-It was also known that when acids and bases were mixed together, some kind of heat producing reaction would happen

-Pure Water -7

-Hydrochloric Acid (HCl) -0 -Sodium Hydroxide (NaOH) -14

-Milk -6.6 -Ammonia -11 -Vinegar -2.2 -Baking Soda -8.3 Guess the pH

-Blueberries -3.1 - 3.4 -Butter -6.1 - 6.4 -Grapes -3.5 - 4.5

http://www.mghs.sa.edu.au/internet/curriculum/science/Year9/Pics/ph.gif

-Acids have always been studied -In 1677 Antoine Lavoisier proposed that oxygen made an acid acidic -derived the name oxygen from greek words meaning "acid former" -In 1808 it was discovered that HCl contains only hydrogen and chlorine -People discovered that hydrogen was the important factor in what made an acid

Conductivity of Water -Ions are needed in a solution to conduct a current -Pure water with no ions would theoretically not conduct electricity at all

Conductivity of Water -However pure water does have a slight conductivity -Svante Arrhenius had the theory that this was due to the presence of ions -Where do the ions come from?

Self-Ionization of Water H2O + H2O > H3O+ + OH− http://honors-chemistry.wikispaces.com/Chapter+15

Keq = [H30]+[OH] [H20]2 At 25 °C Keq is equal to 1.0×10−14

-In this reaction at equilibrium the products are heavily favoured -In 1884 the first modern definition of an acid and a base was given by Svante Arrhenius http://www.magnet.fsu.edu/education/tutorials/pioneers/arrhenius.html

According to Arrhenius... -An acid is a substance that dissociates in water and increases [H3O+] -A base is a substance the dissociates in water and increases [OH] http://studentweb.usq.edu.au/home/W0099066/html/acidbase.html

-According to Arrhenius, when we add an acid to water... http://studentweb.usq.edu.au/home/W0099066/html/acidbase.html

Some common acids What do they all have in common?

According to Arrhenius, when a base is added to water...

Some common bases Sodium Hydroxide - NaOH Potassium Hydroxide - KOH Ammonium Hydroxide - NH4OH Calcium Hydroxide - Ca(OH)2 Magnesium Hydroxide - Mg(OH)2 Barium Hydroxide - Ba(OH)2 Aluminum Hydroxide - Al(OH)3 Zinc Hydroxide - Zn(OH)2 Lithium Hydroxide - LiOH

-BOTH H+ and OH- ions are ALWAYS PRESENT in any solution. -A solution is acidic if the H+ are in excess. -A solution is basic, if the OH- ions are in excess.

Arrhenius also said... -All acids and bases react with each other in the same way - acid + base = salt + water - HCl + NaOH = NaCl + H20

Measuring Acidity and Alkalinity -How do we measure how acidic or basic something is? -We usually measure [H3O+] -Math Review: What is a power? -pH means the power of [H+] -We use logarithms to measure pH -logs are the opposite of exponents the same ways division is the opposite of multiplication

Logarithms - y=bx is the same as logby = x -In pH, b is always 10 -What is: -log101 = -log1010 = -log10100 = -log101000 =

Logarithms -What is: -log100.1 = -log100.01 = -log100.001 =

pH -this is defined as the negative logarithm of the hydrogen ion concentration pH = - log [H+] -Why are we using the negative logarithm?

Example If an acid has an H+ concentration of 0.0001 M, find the pH.

Solution -H+ = 0.0001M = 10-4 -log of 10-4 = -4 -pH = - log [ H+] = - log (10-4) = - (-4) = +4 -The purpose of the negative sign in the log definition is to give a positive pH value.

For each of the following [H+] , calculate the pH: a) 3.28 x10-4 b) 9.43 x10-13 c) 2.71 x10-8 d) 1.00 x10-3 e) 1.00 x10-12

Finish the table H+ pH pOH OH- 1.0 x10-4 3.9 1.2 8.3x10-10

For each of the following pH values, calculate [H+]: a) pH = 5 b) pH = 3 c) pH = 2.8 d) pH = 13.7 e) pH = 6.9

-If pH is based off [H+], is there such a thing as pOH that is based off the concentration of [OH-] -YES, THERE IS!!!!

Find pOH from the following [OH-] -3 x10-3 -9 x10-6 -1 x10-11

-log (3 x10-3) = 2.52 -log (9 x10-6) = 5.05 -log (1 x10-11) = 11

Problems with the Arrhenius idea -Certain substance produce basic solutions and react with acids but don't contain hydroxide ions -An example is ammonia(NH3) http://studentweb.usq.edu.au/home/W0099066/html/acidbase.html

New Theory -In 1923, Johannes Nicolaus Brønsted and Martin Lowry created new definitions for an acid and a base - Brønsted–Lowry acids are hydrogen ion donors - Brønsted–Lowry bases are hydrogen ion acceptors -We call this the Brønsted–Lowry acid–base definition

- An acid can donate a hydrogen ion (a proton) to another substance while a base can accept a proton from another substance Acid Base Donates hydrogen ions Accepts hydrogen ions. HCl+ HOH → H3O+ + Cl- HOH+ NH3→ NH4+ + OH-

-The ion or molecule remaining after the acid has lost a proton is known as that acid's conjugate base -The species created when the base accepts the proton is known as the conjugate acid -acid+ + base- conjugate base- + conjugate acid+ - this reaction can proceed in either forward or backward direction; in each case, the acid donates a proton to the base

Relative Strengths of Acids and Bases -Strong acids are better H+ ion donors than weak acids -Strong bases are better H+ acceptors than weak bases

-HCl is a strong acid and HF is a weak acid -In a dilute solution the ionization of HCl is virtually 100% -Essentially all the HCl molecules react with water

-With HF the reverse of the ionization is significant -the F- readily accepts the H+ from the hydronium -Hydrofluoric acid is mainly unionized in dilute solution

-Strong acids have weaker conjugate bases -Weaker acids have stronger conjugate bases

http://www. sparknotes http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter6section5.rhtml

Bases: 3 ways of OH- formation -Neutral base extraction of H+ from H2O NH3 (aq) + H2O(l) ⇔ NH4+ (aq) + OH- (aq) -Anionic base extraction of H+ from H2O CO32- (aq) + H2O(l) ⇔ HCO3- (aq)+ OH- -Metal hydroxide dissociation to M+ and OH- NaOH (aq) → Na+ (aq) + OH- (aq)

Ka for the following equation HA(aq) + H2O(l) H3O+(aq) + A–(aq)