Acid Base Equilibria and Titrations Flashcards
What are the strong acids
HI
HBr
HCl
HClO3
HClO4
H2SO4
HNO3
(So I Brought No Clean Clothes)
What are the strong bases
Group 1 metal hydroxides
Mg(OH)2
Ca(OH)2
Sr(OH)2
Ba(OH)2
Creating an acidic buffer
Mixing a weak acid and its conjugate base in a 1:1 ratio
Creating an alkaline buffer
Mixing a weak base and its conjugate acid in a 1:1 ratio
Lewis acid
Species that can accept an electron pair
Lewis base
Species that can donate can electron pair
must contain a lone pair of electrons
What are some common Lewis acids?
Metal cations: K+, Mg2+, Ca2+, Fe3+
Neutral compounds of boron, aluminum
Other group 13 elements: BF3, AlCl3
Protons (H+)
What makes a good Lewis acid?
When the central atom can most readily accept an electron pair
Acid/base and conjugate acid/base relationship:
The stronger the acid = the weaker the conjugate base
The weaker the acid = the stronger the conjugate base
The stronger the base = the weaker the conjugate acid
The weaker the base = the stronger the conjugate acid
As pKa/pKb goes down, Ka/kb _______ and acid/base strength ________
As pka/pkb goes up, Ka/kb __________ and acid/base strength _________
Increases, increases
Decreases, decreases
Metal oxides produce ________ solutions in water
Basic
Non-metal oxides produce ________ solutions in water
Acidic
General trend for acidity for oxyacids
- The more oxygen atoms, the more acidic because there are more oxygens for the electrons to spread out onto in the conjugate base
- for oxyacids with the same number of oxygen atoms, acid strength increases with electronegativity: HClO4 > HBrO4 > HIO4
the ______ is placed in an Erlenmeyer flask during a titration
analyte
the _______ is placed in a burrette during a titration
titrant
what is the equivalence point in an acid-base titration?
the point at which the moles of H+ ions in solution is equal to the moles of OH- ions
usually the steepest part of the titration curve
what titrations involve a half-equivalence point?
titrations involving weak acid/strong base or a weak base/strong acid
what is the half-equivalence point in a titration curve?
the midpoint of the buffering region, the part of the curve where the pH of the solution is not drastically affected
what is the process of an acid-base titration?
the concentration of an analyte is determined by gradually adding small volumes of a solution with a known concentration (the titrant). titrant is added until the reaction completes at a certain equivalence point, which can be viewed by color changes or on a graph
at the equivalence point, what formula can be used to determine the concentration of the analyte?
NaVa = NbVb (using normality) or MaVa = MbVb (molarity)
strong acid + strong base = equivalence point at pH
= 7
strong acid + weak base = equivalence point at pH
< 7
weak acid + strong base = equivalence point at pH
> 7
all monoprotic strong acid and strong base titrations will have an equivalence point at pH ______
7
arrhenius acid
any species that dissolves in aqueous solution to produce H+ ions
arrhenius acids are bronsted-lawry acids –> both release protons
arrhenius base
any species that dissolves in aqueous solution to produce OH- ions
formula for calculating pH:
pH = -log[H+]
formula for calculating pOH:
pOH = -log[OH-]
what is the pH of water?
- 7
- it contains the same number of hydrogen ions and hydroxide ions
- [H+][OH-] = (1 x 10-7 M)
what is the constant kw of water?
- water dissociates to produce H+ and OH-
- the constant kw = [H+][OH-] = (1 x 10-7 M)2 = 1 x 10-14
strength of binary acids:
- binary acids: HCl, HBr, HI
- HCl > HBr > HI
- HI is the strongest because it has the largest atomic radius which causes the bond length to become longer and the bond strength to be weaker
neutralization reaction:
- when a strong acid reacts with a strong base to form salt and water
- all protons (H+) and hydroxide ions (OH-) present in the solution combine to form water and the reaction goes to completion
- the salt produced is neutral
reaction that form salts may occur between:
- strong acid and a strong base
- strong acid and a weak base
- weak acid and a strong base
reaction between a strong acid and a weak base:
- results in an acidic salt
- the conj. base of the strong acid is considered to be neutral
- the conj. acid of the weak base is considered to be acidic
- ex: HCl + NH3 -> NH4Cl
reaction between a weak acid and a strong base:
- results in a basic salt
- the conjugate base of the weak acid is basic
- the conjugate base of the strong base is neutral
what formula is used to calculate the pH of a buffer solution?
- Henderson-Hasselbalch equation:
- pH = pKa + log([A-]/[HA])
- [A-] = concentration of conj. base
- [HA] = concentration of weak acid
