Acids
General Weak Acid equation
HA + H₂O ⇌ H₃O⁺ + A⁻
General Base equation
B + H₂O ⇌ OH⁻ + BH⁺
Q: Predict whether the solution of KCN is acidic, basic, or neutral, and explain why.
A: What is basic, because CN⁻ is the conjugate base of the weak acid HCN.
What makes up a Buffer solution
Either a weak base and its conjugate acid, or weak acid and its conjugate base.
This is the solution of known concentration added during a titration
titrant
What are the strong bases
Group 1 (alkali metal hydroxides)
Group 2 (alkaline earth hydroxides)(only if the concentration of the base is less than 0.1 M)
What are the strong bases
HBr – hydrobromic acid
HI – hydroiodic acid
HCl – hydrochloric acid
HNO₃ – nitric acid
H₂SO₄ – sulfuric acid (first proton only is strong)
HClO₃ HClO₄ – chloric acid & perchloric acid
Free 200 points
What is the point of a buffer?
They resist change in pH. Especially when strong acid or base is added to it.
This is the solution of unknown concentration and known volume in the flask.
analyte
Q: The Ka for HF is 6.8×10⁻⁴. Calculate the pH of 0.10 M NaF.
→ pH ≈ 8.08
A buffer resists pH change best not when one component dominates, but when the acid/base ratio is closest to this number.
1
At the equivalence point of a weak acid–strong base titration, all HA has been converted into this species
A⁻, the weak conjugate base
For a salt made from a weak acid and a weak base, such as ammonium acetate (NH₄CH₃COO), the solution is acidic when this inequality is true.
Ka of the cation > Kb of the anion
A weak base is titrated with a strong acid. Titration ends exactly at the equivalence point. What is the pH of the solution. Explain why for full points.
Acidic
Q: A solution contains 0.10 M NaHCO₃. This salt can act as both an acid and a base. Predict whether the solution is acidic, basic, or neutral, and justify.
Ka₁ (for H₂CO₃) = 4.3 × 10⁻⁷
Ka₂ (for HCO₃⁻) = 4.8 × 10⁻¹¹
A: Slightly basic, because HCO₃⁻ has both Ka (acidic) and Kb (basic) behavior, but Kb > Ka.
A polyprotic acid is titrated by a strong base. How many equivalents of base are needed so that pH = pKa3
2.5