Water & pH Flashcards
Cation vs anion
loss of electron, positive charge
Gain of electron, negative charge
Polar vs nonpolar covalent bonds
Polar- Electrons are shared unequally, resulting in one atom with a partial positive charge and one with a partial negative charge. Ex: water
Nonpolar- Electrons are shared equally, electronegativities of the 2 atoms are equal. Ex: Carbon and hydrogen
Electronegativity trend
Increases as you go right. Increases up.
The concentration of hydrogen ions produced by dissociation in pure water is
1 x 10^ -7 M
Molarity
Moles of solute per liter of solution (mol/L)
1 mole= 6.02x 10^23
Acidic solutions have more __ and less __
Basic solutions have more ___ and less __
Acidic- more H+, less OH-
Basic- More OH-, less H+
Solutions are classified as acidic or basic based on their ___ concentration relative to pure water
Hydrogen ion
pH stands for
The power of H. How the hydrogen ion concentration of a solution is expressed.
Equation for pH
pH = -log [H+]
H+ can either be in the 1x10^x form or M
Strong acids or strong bases in water
Completely dissociate. Reaction goes one way. No going back.
Weak acids or bases in water
Incompletely dissociate. Can interconvert between acidic and basic forms as conditions change
Define an acid and a base
Acid gives away H+. An acid added to an aqueous solution increases the H+ concentration by giving away H+. The freed H+ combines with water molecules to form Hydronium (H3O+)
Bases bind to H+. Bases added to an aqueous solution decreases H+ concentration by binding their lone pair of electrons with H+.
HA + H2O H3O+ + A-
Weak acid (HA) + water dissociates into hydronium and a conjugate base.
B + H2O BH+ + OH-
Weak base plus water dissociates into a conjugate acid and OH-.
Ka (Kb) and pKa
Value used to describe the tendency of compounds to dissociate in water (the dissociation or equilibrium constant).
More comply expressed in log measures (pKa) due to many orders of magnitude spanned by Ka values.
pKa equation
pKa= -log ( [H+] [A-] ) / [HA]
-log (product concentration) / weak acid reactants
pKa is a given constant
Tip: anything with a P= negative.
What can act as buffers?
Weak acids and weak bases
What do buffers do
They resist changes in pH when small quantities of acid or base are added to the solution.
Buffers can both bind or release proteins and, in doing so, prevent the pH from changing rapidly.
How do weak acids react when strong bases are added
Strong bases (OH-) will bind to the hydrogen of the weak acid (HA) or conjugate acid produced by the weak base (HB) and produce water
This will create water and A- or water and
How do weak bases react when strong acids are added
The weak base (B-) or conjugate base from a weak acid (A-) can neutralize any H+ (strong acid) added to the system to create HB or HA.
When is a buffer at optimal strength
When there are equal amounts of HA and A- (weak acid and conjugate base). This occurs when pH= pKa
What equation is useful for estimating the pH of a buffer solution
Henderson-hasselbalch
pH= pKa + log ([A-]/[HA])
pH of blood
7.4
Metabolic acidosis and metabolic alkalosis
Metabolic acidosis is 7.35 or below. Results in coma or death.
Metabolic alkalosis is 7.45 or above. Results in confusion and convulsions.
4 categories of buffers
Proteins,phosphates, carbonic acid/bicarbonate, and respiratory and renal system also regulate acid-base balance.
Where are protein buffers found
In blood plasma and cells. Nearly all proteins can function as buffers because the carboxyl functional group acts as a weak acid and the amino functional group acts as a weak base.
Buffering by proteins accounts for ___ of the buffering power of the blood and ___ of the buffering within the cells
2/3
most
Phosphate buffer weak acid and conjugate base
Weak acid- dihydrogen phosphate
Conj base- Monohydrogen phosphate
Carbonic acid is the __ and bicarbonate is the ___
Weak acid, conjugate base
Usually, ____ in the body function as buffers
Weak acids
