Note Guide 10-2 Hydrogen Ions from water (water molecule highly polar) --A water molecule that loses a hydrogen ion becomes a negatively charged hydroxide ion (OH - ). --water molecule that gains a hydrogen ion becomes a positively charged hydronium ion (H 3 O+) --when molecules produce ions we call this reaction self- ionization of water H 2 O(l) H + (aq) + OH - (aq) Hydrogen ion Hydroxide ion

--self ionization of water occurs to a small extent. --pure water at 25°C is at equilibrium between concentrations of [H+] and [OH - ] (1 x10 -7 ) --any solution in which [H + ] and OH - ] are equal is called neutral solution Ion Product constant for water --when [H+] increases, [OH - ] decreases and vice versa H + (aq) + OH - (aq) H 2 O (l) --for aqueous solutions, the product of the hydrogen-ion concentration and the hydroxide ion concentration equals 1.0 x

[H + ] x [OH - ] = 1.0 x equation OK dilute (aq) solutions at 25°C --product of the concentrations of the hydrogen-ion and hydroxide-ions in water = ion-product constant for water (K w ) K w = [H + ] x [OH - ] = 1.0 x not all solutions are neutral, some, like HCl (hydrochloric acid, have a greater hydrogen-ion [H + ] concentration than hydroxide ion [OH - ] concentration = acidic solution --[H + ] > 1 x10 -7

--when hydrogen ion [H + ] concentration is less than the hydroxide ion [OH - ] concentration it’s a basic solution (also called alkaline solutions) EX: Sodium hydroxide (NaOH) --[H + ] < 1 x we can find the [OH - ] of a solution See sample problem page 596 pH concept --scale used to check acidity: (0-14) whereas 0 is strongly acidic, 7 is neutral, and 14 is strongly basic pH is negative logarithm of the [H + ] concentration pH = -log[H + ]

--solution in which [H + ] is greater than 1 x10 -7 M has a pH less than 7.0 = acidic --solution in which [H + ] is less than 1 x10 -7  pH < 7.0 [H + ] is greater than 1 x10 -7 M  pH = 7.0 [H + ] equals 1 x10 -7 M  pH > 7.0 [H + ] is less than 1 x10 -7 M

A Lewis acid is a substance that can 1.Accept a hydrogen ion 2.Donate a hydrogen ion 3.Accept a pair of electrons 4.Donate a pair of electrons

What is pH? 1.The + log of the hydroxide ion concen. 2.The – log of the hydroxide ion concen. 3.The – log of the hydrogen ion concen. 4.The + log of the hydrogen ion concen.

What is transferred between a conjugate acid-base pair? 1.An electron 2.A hydronium ion 3.A hydroxide ion 4.A proton

The formula of the hydrogen ion is often written as 1.OH + 2.H + 3.H 4 N + 4.H 2 O +

Note Guide 10-2 day 2 --the hydrogen-ion concentrate of a solution is used to classify the solution as acidic, neutral, or basic.

--common pH values

Calculating pH from [H+] --when we know the amount of hydrogen-ion concentration, we can find out what the pH is.  pH = -log[H+] See sample problem 19.2 pg. 599 and do 11 and 12 Calculating [H+] from pH -- we can find out what the hydrogen-ion concentration is in a solution if we know the pH.  -log[H+] = pH see sample problem 19.3 pg. 600 and do 13 and 14 Measuring pH -- knowing the pH of a solution is important in everyday life. EX: soil needs the right pH to grow plants…swimming pools

Calculating pH from [OH - ] --first step involves finding out what the H+ concentration is: Kw = [OH-] x [H+] --with [H+] calculated, now use pH = -log[H+] See sample problem 19.4 and do 15 and 16