Miscell-aneous
What is the conjugate base that is formed when carbonic acid (H2CO3)is dissolved in water?
HCO3-
Acid: H₂CO₃
Conjugate base: HCO₃⁻
Reason: It forms after H₂CO₃ donates a proton to water.
This is the product formed when an acid reacts with a base. (BONUS 100 if you know why)
A salt (and water)
In a neutralization reaction, the H⁺ from the acid combines with the OH⁻ from the base to form H₂O, leaving the remaining ions to form a salt.
When HCl donates a proton (H⁺), what’s its conjugate base?
Cl-
HCl is a strong acid that donates an H⁺ ion, leaving behind Cl⁻. The conjugate base is always what remains after the acid loses a proton.
Acid strength generally increases in this direction across a period. (BONUS 100 if you can tell back)
Left to right
Electronegativity increases, making the H–X bond more polar and easier to lose H⁺.
The equilibrium constant for acid ionization is symbolized by this.
Ka
When titrating a weak acid with a strong base, approximately where would the pH be observed when reaching the equivalence point?
At the equivalence point, the pH is greater than 7
Weak acid + strong base → equivalence point is basic, because the conjugate base of the weak acid produces OH⁻.
This type of solution is formed when a strong acid reacts with a strong base.
Neutral solution
Strong acids and bases completely neutralize each other, producing water and a salt that does not hydrolyze, resulting in pH ≈ 7.
Identify the conjugate acid of NH₃.
NH4+
NH₃ (ammonia) acts as a base because it accepts a proton (H⁺). When it does, it forms NH₄⁺ (ammonium). Adding an H⁺ makes the conjugate acid.
Acid strength increases down a group because this happens to bond strength. (BONUS 100 if you can answer the why)
It decreases
Larger atoms form weaker H–X bonds, allowing hydrogen to ionize more easily.
The higher the Ka, the ______ the acid.
Stronger
A larger Ka means greater ionization and more H⁺ ions in solution.
Which one of the following combinations cannot form a buffer solution?
HNO3 and LiNO3
HNO₃ is a strong acid → it completely ionizes in water:
HNO₃ → H⁺ + NO₃⁻
LiNO₃ is the salt of a strong acid (HNO₃) and strong base (LiOH) → it does not hydrolyze in water and has no ability to accept or donate protons.
Because both HNO₃ and LiNO₃ are strong (fully dissociated), there is no weak acid/conjugate base pair present. Therefore, the solution cannot resist pH changes when additional H⁺ or OH⁻ is added.
How many strong bases are there and what are they?
6; LiOH, NaOH, KOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂
*** Remember Little (LiOH) Naughty (NaOH) Kids (KOH) Can’t (Ca(OH)₂) Stay (Sr(OH)₂) Behaved (Ba(OH)₂)
H₂O can act as both an acid and a base. When it acts as an acid, what is its conjugate base?
OH-
When water donates a proton (H⁺), it becomes hydroxide (OH⁻). Because it loses a proton, OH⁻ is the conjugate base of H₂O.
Between HF and HI, which one is the stronger acid and why?
HI
Although fluorine is more electronegative, the H–I bond is much weaker, so HI dissociates more easily.
The product of Ka and Kb for a conjugate acid–base pair equals this constant
Kw (1 × 10⁻¹⁴)?
For any conjugate pair, Ka × Kb = Kw; this maintains equilibrium between acid and base forms.
When a solution of sodium cyanide (NaCN) is poured into excess hydrochloric acid, this molecule is formed.
HCN (hydrocyanic acid)
CN⁻ is the conjugate base of HCN. When it reacts with H⁺ from HCl, it picks up a proton to form HCN. This demonstrates a conjugate acid-base reaction outside water.
How many strong acids are there and what are they?
7; HClO₄, HClO₃, HCl, HBr, HI, H₂SO₄, HNO₃
***Remember I (HI) Brought (HBr) No (HNO₃) Clean (HCl) Colorful (HClO₄) Clothes (HClO₃) Sir (H₂SO₄)
The conjugate base of H₂CO₃ (carbonic acid) is _______.
HCO₃⁻ (bicarbonate)
H₂CO₃ donates one proton (H⁺) to form HCO₃⁻. The difference between them is exactly one hydrogen and one positive charge, which is a perfect example of an acid–base conjugate pair.
Order these from weakest to strongest: H₂O, H₂S, H₂Se, H₂Te.
H₂O < H₂S < H₂Se < H₂Te
Down the group, bond strength weakens, so acid strength increases.
The conjugate base of a weak acid is typically ______.
Relatively strong
Weak acids hold onto protons tightly, so their conjugate bases are better at accepting them.
This happens to the pH of a solution when a weak acid is diluted.
The pH increases slightly (becomes less acidic)
Diluting a weak acid shifts its ionization equilibrium slightly to produce more H⁺, but because the solution is more dilute overall, the [H⁺] decreases, so the pH rises.
When 0.50 moles of HCl are mixed with 0.25 moles of NaOH, the resulting solution is typically this.
Acidic
There is excess acid (0.50 – 0.25 = 0.25 moles of HCl left), so H₃O⁺ is present in solution, making it acidic.
Identify the conjugate acid–base pairs in this reaction:
H₂PO₄⁻ + H₂O ⇌ H₃O⁺ + HPO₄²⁻
Conjugate pairs: H₂PO₄⁻ / HPO₄²⁻ and H₂O / H₃O⁺
H₂PO₄⁻ donates a proton to become HPO₄²⁻ → it’s the acid, and HPO₄²⁻ is its conjugate base.
H₂O accepts that proton to become H₃O⁺ → it’s the base, and H₃O⁺ is its conjugate acid.
This shows both acid–base pairs differ by one H⁺ each.
Between HBr and AsH₃, which one is the stronger acid and why.
HBr, because H–Br bonds are more polar and easier to break.
Bromine is more electronegative and forms a weaker bond with hydrogen, favoring dissociation.
Buffers resist pH changes because they contain these two components.
A weak acid and its conjugate base (or vice versa)
The weak acid neutralizes added base, and the conjugate base neutralizes added acid, maintaining near-constant pH.