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Ch. 16 - Coggle Diagram
Ch. 16
AUTOIONIZATION, THE CRUX:
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All aqueous BL reactions work off of these concentrations in such a way that [OH-][H3O+] = 10^-14 is MAINTAINED NO MATTER WHAT ("constancy of Kw.")
Due to log rules, since [OH-][H3O+] = 10^-14, log of both sides yields log[OH-] + log[H3O+] = -14. Applying a negative and translating to P gives pOH + pH = 14.
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Conversion to and from [H+] and pH, from [OH-] and pOH, pH and pOH, and [H+] and [OH-] (remember constancy of Kw) called the BL SQUARE... CRUCIAL FOR CALCULATIONS
Also, when you combine a conjugate acid/base reaction equations, you end up with [H+][OH-]... which we know has a K of 10^14. Due to K properties, the Ka and Kb of those conjugates MUST MULTIPLY TO 10^-14.
BASIS OF ACID-BASE:
Bronsted-Lowry says that acid vs. base is TENDENCY TO DONATE OR ACCEPT PROTONS. (mechanism of which we didn't go over.)
The character that donates or accepts the proton, or the conjugate acid/base, RETAINS this tendency.
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Remember every acid-base interaction is an EQUILIBRIUM REACTION; just depending on the strength, may be very right or left-sided
WEAK ACIDS/BASES:
Unless Ka/b is stronger than usual, ASSUME that initial concentration of weak BL won't change due to sig fig subt.
APPROACH: Start with chemical equation --> ECE, and initial concentrations, Ka, anything else. GO TO ICE TABLE, AND PLUG IN VALUES FOR ECE.
Weak acids:
POLYPROTICS: subsequent protons are harder to pull off, due to negativity (intuitive); Ka2, a3 are lower than Ka1.
PERCENT IONIZATION: AS CONCENTRATION INCREASES, PERCENT IONIZATION DECREASES!!!! Due to less water molecules per molecule of weak acid. (le chat's?)
Weak bases:
Either conjugate of weak acid, or nitrogenous compound that is either NH3 or an amine (thing w/N-C bond). Since N confers a lone pair.
STRONG ACIDS/BASES:
Acids:
ALL HALOGENIC ACIDS EXCEPT FOR HF, due to its H bonds and F's strong electronegativity
Oxyacids: If difference between H and O atoms at least 2, STRONG ACID. (FE)
Bases:
All group 1 hydroxides, heavy group 2 (Ca, Sr, Ba) hydroxides
NOTE: technically strong arrhenius bases; but still increase concentration of OH- due to salt nature.
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IMPORTANT IDEAS:
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Acid-base reactions are equilibrium (reversible) reactions. Always be thinking in terms of forward and reverse, and K as an equilibrium constant which can tell you sidedness.
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SALT PROPERTIES:
Consider cation + anion of salt as conjugate acids/bases... then discern strength based maybe off THEIR conjugates
Metal ions except for those on the strong bases (G1, G2 heavy) MAKE MORE ACIDIC.
If both may affect, whichever affects more depends on their strength (Ka vs. Kb.)