Acid Base Chemistry Flashcards
Any molecule that donates H+ in aqueous solution?
Acid
Any molecule that accepts H+ in aqueous solution?
Base
Any molecule that donates an electron pair in aqueous solution?
Lewis Base
Any molecule that accepts an electron pair in aqueous solution?
Lewis Acid
In a polyprotic strong acid, how do the H+ dissociate?
They dissociate together
What is normality?
A normal is one gram equivalent of a solute per liter of solution.
Ex: hydrochloric acid is a strong acid that dissociates completely in water, a 1 N solution of HCl would also be 1 N for H+ or Cl- ions for acid-base reactions.
How would you calculate the normality of a polyprotic strong acid?
([H+]/liter of solution) x however many protons dissociate
5 mM can also be written how?
(5 x10^-3M)
How would you calculate the pH of a diprotic strong acid, such as H2SO4?
multiply the concentration of the H2SO4 solution by 2 (because 2 protons are dissociating) to get [H+], then use pH= -log[H+]
If the concentration of H+ was 1 x 10^-2, what would the pH be?
pH = -log(1 x 10^-2) = 2
What is the formula used to calculate pH?
pH = -log[H+] or pOH = -log[OH-]
What is the formula used to calculate the ion product of water?
[H+][OH-] = 10^-14 so [H+] = [OH-] = 10^-7
*true for all aqueous solutions
A reaction that goes to equilibrium is called what?
reversible reaction
ex: ionization of water
How do you calculated the equilibrium constant?
Keq = [products]/[reactants] = [C][D]/[A][B]
Molecules that partially dissociate and individual protons dissociate at a different time and to a different extent?
weak polyprotic acids
When an acid donates a proton, what does it become?
conjugate base [A-]
When a base accepts a proton, what does it become?
conjugate acid [B+]
A reaction containing an acid that dissociates can be defined as what?
acid-conjugate base pair
To measure the amount of dissociation of an acid what steps would you take?
-define equilibrium constant Keq = [H+][A-]/[HA] = Ka -use pKa to determine [A-] pKa = -log[A-] so Ka = 10^-pKa = [H+][A-]/[HA] *energy is neither created or destroyed, so [H+]=[A-] so (10^-pKa)[HA]=[H+]^2 -then use [H+] to calculate pH pH = -log[H+]`
Process by which an acid is converted to a conjugate base in a step-wise procedure by addition of known concentration of titrant?
titration
What is the half equivalence point?
moles of analyte = moles of conjugate acid/base
-point when half of the analyte has dissociated and so for an acid titration, [H+] = [HA]. The concentration of titrant added at half equivalence point is only half the concentration of analyte originally present. Therefore, at half-equivalence; pH = pKa.
What is the equivalence point in a titration?
moles of titrant = moles of analyte.
-point at which the concentration of analyte (could be acid or base) is equal to the concentration of titrant because the analyte has completely dissociated
What is the midpoint in a titration?
Same as half equivalence point
What is the isoelectric point in a titration?
-point at which the polyprotic acid has dissociated and now has no net electrical charge
How do you calculate the isoelectric point, pI, for a polyprotic acid
take the average of the 2 or more dominating pKa’s (for acids, only calculate the acids pKa’s
What is the significance of the isoelectric point?
it is the point at which a polyprotic acid is least soluable in blood and electrolytes in the blood will associate with the acid and precipitate
Weak acid-conjugate base pairs that resist changes in pH when small amounts of acid or base are added to solution are called what?
buffers
What are buffers?
Weak acid-conjugate base pairs that resist changes in pH when small amounts of acid or base are added to solution
Molecules with pKa’s in what range make good physiologic buffers?
6-8 such as histidine
Henderson-Hasslebach
pH=pKa + log [A-]/[HA]
