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29 Cards in this Set
- Front
- Back
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Acid
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H+ donor
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Base
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H+ acceptor, or an -OH donor
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Strong acid vs weak acid-base conjugate
HCI vs. CH3COOH (acetic acid) |
Strong Acid - dissociates completely in water (High [H+])
Weak acid-base conjugate does NOT dissociate completely in water HCI dissociates completey if reacted with a strong base (KOH) then 1 mol -OH reacts with 1 mol H+ With CH3COOH conjugate base CH3COO- do not completely dissociate- make good buffer |
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pH
Change in H+ concentration when pH is raised from 6.5 to 7.5? |
= -log [H+], as the [H+] increase the pH is lower
A: 7.5-6.5 = 1, 1 = - log [H+], change in [H+] = 10 |
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Ka
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Equilibrium constant for inoization reaction - the tendency of any acid, HA, to lose a proton and form a conjugate base, A-, is defined by the equilibrium:
HA -> H+ + A- Ka = [H+] [A-] / [HA] |
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pKa
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= - log Ka
The strong teh tendency to dissociate a proton the stornger the acid and LOWER its pKa |
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Ka of weak acid is 1.0x10^(-5)
pKa? |
= - log (1.0x10^(-5)
= 5 |
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Hendersen - Hasselbalch
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Weak acid/conjugate base
pH = pKa + log ( [proton acceptor] / [proton donor] ) or pH = pKa + log ([A-] / [HA]) fits the tirtration curve of all weak acids, pKa = pH at the midpoint of titration curve (also where [HA] = [A-]) |
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If pKa of dissociable group is 6.5, what percentage of the compound is in the dissociated form at pH 7?
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7 = 6.5 + log ([proton acceptor] / [proton donor])
3.16 = [PA]/[PD] ~75% |
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Ion product of water
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Kw
Kw = [H+][OH-] = 1x10^(-14) Kw is always constant, a dcrease in [H+] is accompanied by an increase in [OH-] |
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What is the [H+] in solution of 0.01M KOH?
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pH = 12
pOH = -log (1x10^-2) pOH = 2 14-2 = 12 |
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Buffer
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causes a solution to resist changed in pH when -OH or H+ is added
they react with additives to form water. The more buffer ins olution means more resistance to change |
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Better Buffers, weak acids or strong acids?
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Weak acids better buffers because they only partially dissociate, this allows they to resist change in both increasing and decreasing pH conditions.
-Strong Acids and Bases only resist change in one direction, increasing pH and decreasing pH respectively |
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Titration, what is it?
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Add base to a particular acid to determine: concentration, or pKa of the acid
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Flat zone of a titration?
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Represent Weak Acid titration, where [HA] = [A-]
-50% of acid is dissociated, pH=pKa |
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pKa to buffer ability
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Weak Acid buffer region: +1 and -1 of the pKa.
ex: pKa = 4.7 buffer zone: 3.7 - 5.7 |
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Biological buffers in body?
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- Bicarbonate buffer system (extracellular fluid)
-hemoglobin buffer system (red blood cells) -Phosphate buffer system (all types of cells) - Protein buffer system (cell and plasma) |
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How can CO2 help buffer in the body?
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It's an open system so the suppy of CO2 can be controled
H+ -> HCO3 - ->H2CO3 -> CO2 + H20 As base is added teh H+ is removed, H2C03 dissociates into hydrogen and bicarbonate ions to maintain equilibrium in teh above equation. Since teh H2CO3 have decreased, dissolved CO2 reacts with H2O to replenish the H2CO3 |
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open system vs. closed system
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Open system sremove an unwanted product via breathing. By removing the carbon dioxide product in teh equilibrium equationa bove Le' Cheutelie's princile drives the equation to the right and removes the acid from the blood, thus maintaing the pH within healthy levels.
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Covalent bonds
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there is a SHARING of electrons
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Noncovalent bonds
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electrons are NOT shared
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why do noncovalent bonds break and reform more readily?
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covalent bonds involve Sharing Electrons are more difficult to break and refrom then non-sharing
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Non-Covalent forces (4)
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1. electrostatic (ionic)
2. Van Der wall forces 3. Hydrophobic interactions 4. Hydrogen bonding |
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Hydrophobic interactions
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Hydrophobic molecules aggregate/cluster together in hydrophilic environments
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Van Der Wall Forces
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Weak attrachtions based on induced dipole
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Hydrogen Bonding
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relatively strong bonds between H+ and F,O, or N due to parital charges indcued by polar covalent bonds.
Seen in water molecules. The O can be a h-bond acceptor, and the H are h-bond donors (dipolar nature) |
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electrostatic/ionic bondig
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a chemical bond in which one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion
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polar vs. non-polar
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polar - electronegative difference between to atoms in a molecule. Alkanes are non-polar (molecules compose of CH, as well as symetrical molecules)
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Aliphipathic
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"having a duel nature" - have both hydrophobic and hydrophilic portions. Ex: phospholipids have polar head and nonpolar tail. Pospholipids interact with water by orienting its hydrophilic "head group" towards water and isolating its nonpolar (aliphatic) tail from water - lipid bilayer
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