Acid Base Flashcards
Water Electron Shell
Electron shell: inner shell has two valence electrons, outer shell has 6 –> always wants outermost shell full so combines with H+ (covalently bonded bc share electrons)
Principle Chemistry of Water
- Simple triatomic molecule
- Molecules in constant motion –> Brownian motion
- Attract each other, form hydrogen bonds
- Occasional proton (H+) transfer when collision occurs, resulting in hydronium ion (H3O+) or some relative (H9O4+)
- Key = transfer of positive charge
- Partially negative at O end due to lone electron pairs, partially positive at H end
Water Molecule Anatomy
Distance btw O and H is 95.84 picomoles
Angle btw two hydrogen molecules is 104.45* - should be 109* but H molecules pushed closer together by lone electron pair
1 mole
6.023 x 10^23 particles
H20 Dissociation
Slightly dissociates into H and OH (hydroxyl) ions
This tendency to dissociate is described by:
Keq x [H20] = [H+] x [OH-] @ 25C
**Concentrations of each ion only 1 x 10^-7 mmol/L (M) @ 25*C or 1x10^-14 M total ions
Molarity of pure water (neutral)
55.5M
[H] = [OH]
Water Dissociation Constant (Kw’)
Keq x [H20] = Keq x 55.5M = Kw’
Kw’ = [H+] x [OH-] = 1 x 10^-14
Kw’ dictates the relative concentration of [H] and [OH] are constant
Acidic Solution
[H+] > 1 x 10^-7M
Basic Solution
[OH-] > 1 x 10^-7M
If H+ is 1.0M, what is OH?
OH = 1.0 x 10^-14 –> acidic solution
If H+ is 1.0 x 10^-3M, what is OH?
OH = 1.0 x 10^-11 –> acidic solution
If H+ is 1.0 x 10^-7M, what is OH?
OH = 1.0 x 10^-7 –> pure water
If H+ is 1.0 x 10^-10M, what is OH?
OH = 1.0 x 10^-4 –> basic solution
If H+ is 1.0 x 10^-14M, what is OH?
OH = 1.0M –> basic solution
If OH- is 1.0 x 10^-14M, what is H+?
H = 1.0M –> acidic solution
If OH- is 1.0 x 10^-11M, what is H+?
H = 1.0 x 10^-3M –> acidic solution
If OH- is 1.0 x 10^-4M, what is H+?
H = 1.0 x 10^-11M –> basic solution
If OH- is 1.0M, what is H+?
H = 1.0 x 10^-14M –> basic solution
Arrhenius Acid
Any substance that delivers an H+ into an aqueous solution
- In an aqueous solution: H20 + H+ –> H3O+
- Or: HCl + H20 –> H3O+ + Cl-
Arrhenius Base
Any substance that delivers an OH into an aqueous solution
-In an aqueous solution: NaOH + H3O+ –> Na + 2H20
H20, Acid-Base Dissociation
H20 = highly ionizing –> substances with polar bonds dissociate well in it
- Degree of ionization determines whether an ion is strong
- Strong ions completely dissociate –> free in solution
- Weak acids/bases ionize only partially
Examples of Arrhenius Acids
Cl-, Lactate-, ketones-, sulfate-, formate
Cause retention of H+ to maintain electroneutrality
Examples of Arrhenius Bases
Na+, K+, Ca2+, Mg2+
Cause retention of OH- to maintain electroneutrality
Bronsted-Lowry Acids and Bases
Expanded definition of AB in 1923
Not all bases have hydroxyl group (OH)
Ex: NH3, NaCO3
Bronsted-Lowry Acid
Any substance capable of donating H+
Must have H+ in its structure
Bronsted-Lowry Base
Any substance capable of accepting H+
Water and BL AB
Water = amphoteric –> can act as a BL acid and a BL base
Conjugate Base of a BL Acid
Substance formed after acid donates H+
HA + B –> A- + BH+
A- = conjugate base
BH+ = conjugate acid
Conjugate Acid of a BL Base
Substance formed after base accepts H
HA + B –> A- + BH+
A- = conjugate base
BH+ = conjugate acid
Hydrogen Ions
Important electrolytes (Na, Mg, K) are measured in mEq/L but H+ measured in nEq/L
Why H+ problematic:
- Very reactive
- Proteins have dissociable groups that gain/lose H+ if {h} changes, affecting structure and function
[H] compatible with life
16-160 nEq/L
What concentration of [H+] corresponds to a pH of 7.4?
Normal [H+] @ pH = 7.4 = 40nEq/L
= 0.0000004 Eq/L
= 4 x 10^-8 Eq/L
What pH range is compatible with life and what hydrogen concentration correlates with those pHs?
pH makes it seem as though [H+] more tightly controlled than it is
pH range compatible with life: 6.9-7.5
[H+] 32-125 nEq/L
Law of Mass Action
rate of a chemical reaction is directly proportional to the product of activities/concentration of the reactants
Write the derivation of the law of mass action
ADD PICTURE
Ka
Ionization/dissociation constant
Larger Ka = Larger K1 = stronger acid –> more [H+], [A-], and more dissociation
Smaller Ka = Larger K2 = weaker acid –> more [HA], less dissociation
Directly proportional to temp: increased T –> increased Ka –> increased dissociation
Draw the derivation of the Henderson-Hasselbach equation
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Henderson-Hasselbach
pH = pKa + log [A-]/[HA]
If pH is lower in the ECF…
meaning that the [H+] is higher than the pKa, then the compound will be protonated ie the more protonated compound will exist more than the unprotonated/dissociated compound
If pH is higher in the ECF…
meaning that the [H+] is lower than the pKa, then the compound will be deprotonated
Le Chatelier’s Principle
AKA Equilibrium Law or Chatelier’s Principle
-When a system experiences a disturbance (ie concentration, temperature, pressure changes, etc) will respond to a new equilibrium state
