CHMA11 (Chem 2) Textbook Notes for Chapters 15-18

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23 Apr 2012
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Chma11 Textbook Notes
15.2
Properties of Acids
-ability to dissolve many metals, - sour taste, -turn litmus red, titrate to clear
Properties of Bases
-bitter taste, feel slippery, turn litmus blue, titrate to pink
-“alkali”, “alkaloids” = bases! Organic bases specifically
15.3
Arrhenius Definition
-Acid = substance that produces H+ ions in aq
-Base = substance that produces OH- ions in aq
*H+ ions associate with H2O to form H3O+, hydronium ions
Bronsted-Lowry Definition
-Acid = proton (H+) donor
-Base = proton (H+) acceptor
-under this def’n, proton donors and proton acceptors always occur together
-amphoteric = a substance that can act as acids or bases. Ex. Water
-in the reverse eq’n, the base that has now accepted a proton can act as an acid. And, the acid that has
donated a proton can now act as a base.
-these pairs that are exactly one proton off are conjugate acid-base pairs
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15.4
*The stronger the acid, the weaker the conjugate base*
-the strength of an electrolyte is determined by how much it dissociates/ionizes
-complete ionization indicates the equilibrium lying far to the right (indicated by a single arrow rather
than the reverse, forward double llbm arrows) and a strong electrolyte
-6 important strong acids: HCl, H2SO4, HNO3, HBr, HI, HClO4
-monoprotic acid = only one ionisable proton Ex. HCl
-diprotic acid = two ionisable protons Ex. H2SO4
15.5
-autoionization: the process of pure water acting as an acid and a base with itself
-We quantify the autonization of water with the llbm constant, Kw = the ion product constant for water
= the dissociation constant for water
*In pure water=neutral=[H3O+] and [OH-] are equal=Kw= 1.0 x 10-14 *, true at standard conditions (2C)
-The individual concentrations of [H3O+] and [OH-] will be 1.0 x 10-7
-Even in acidic or basic solutions, ion product constant still applies, just the relative conc’ns will differ
*Sig figs:
* Ka = pKa acid strength = [H3O+] = pH towards 7 = pOH towards 7
-since it depends on llbm, we quantify
strength with Ka = acid ionization
constant = llbm constant
*[H3O+] = [H+]*
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15.6
-for a strong acid, [H3O+] = [strong acid]
-for weak acids, we need to use their Ka and make an ICE chart
Solving for x will allow us to find [H3O+] and then get the pH
If it is not a valid assumption, you must use the quadratic formula x =
-% ionization =
-in a mixture of acids, the contribution of hydronium from the weaker is negligible so realy we only need
to consider the stronger acid
(for two week acids, compare their Ka and only consider the one with the larger Ka
15.7
-The 6 common strong bases are Li, Na, K, Sr, Ca, and Ba hydroxides
(i.e. Group 1, group 2 metal hydroxides)
Small x approximation:
You suppose that 0.10-x will be
virtually = 0.10
Then, when you actually find x with
this method, you divide your x/0.10
and make sure that the number you
get is less than 5%
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