Acids and Bases
What is a weak acid?
An acid that does not dissociate completely.
Give an example of a weak base.
NH3 (Ammonia), H2O (water)
What is an acid-base indicator? What color does phenolphthalein turn in basic solution.
A special dye or pigment that changes color based on pH change. Example: phenolphthalein goes from colorless to pink.
What is the equilibrium expression (Keq)
Keq = (products)/(reactants)
What happens to solubility as the temperature increases?
It increases, generally.
Describe the Bronsted-Lowry definition of acids and bases.
Acid is a proton (H+) donor and base is a proton (H+) acceptor.
What is a buffer?
A combination of weak acid/conjugate base or weak base/conjugate acid.
What is the equivalence point in a titration?
The volume at which moles acid = moles base.
How do you calculate Kb from Ka (at 25C)?
Kw = 1.0*10^-14 at 25C.
Kb=(1.0*10^-14)/Ka
What is the molar solubility of CaCO₃ given Ksp = 4.0 × 10⁻⁹?
Ksp = x2
Square root (4.0*10^-9) = x
x = 6.32*10^-5
Name the strong acids
HCl, HBr, HI, HNO3, HClO4 , H2SO4
What is the Henderson-Hasselback Equation?
H-H equation: pH= pKa + log (A-)/(HA)
Describe the pH change during a strong acid-strong base titration. What is the expected equivalence point pH?
The expected EQ pH is pH= 7.00.
What is the expression for Ksp for general solid metal halide MX (s)?
Given MX (s), the Ksp expression is Ksp = (M+)(X-)
How does pH affect solubility
pH affects solubility because a lower pH increases the concentration of H⁺ ions, which can shift equilibrium to favor dissolution.
Name the strong bases.
Group I and heavy II's (Ca, Sr, Ba, etc) and OH.
How does a buffer maintain pH?
When you add H+, it reacts with the conjugate base and creates more weak acid keeping the pH stable.
How do you determine the pH past the equivalence point?
What is the common ion effect?
A given solution with a given concentration has an ion in common (usually the conjugate ion). You use this concentration in the ICE table instead of 0 for the initial.
What is the Ksp for Mg(OH)₂ if its molar solubility is 0.010 M?
If the molar solubility of Mg(OH)₂ is 0.010 M, then Ksp = [Mg²⁺][OH⁻]².
Ksp=(0.010)(2(0.010))2=4.0×10−11Ksp=(0.010)(2(0.010))2=4.0×10−11
What is the difference between a monoprotic and diprotic acid?
Mono-protic acids only have one ionizable hydrogen. Diprotic acids have two ionizable hydrogens.
What is the buffer region of a titration and how do you calculate the pH here?
This is the half-equivalence point, where pH = pKa.
Calculate the pH of a solution after adding 10 mL of strong base to 10 mL of 0.15 M strong acid. Use M1V1 = M2V2.
(0.15)(10)= M2(20)
M2= 0.75 M
What does it mean if Q > Ksp?
The reaction shifts to the left. The product will precipitate.
How can you selectively pick a substance to precipitate based on Ksp?
Compare Ksp values for your solids to Q to determine the shift. If Q is greater than Ksp, it will precipitate.