Buffer or not?
HNO₃ / NaNO₃
Not a buffer because HNO₃ is a strong acid even though there is a common ion.
HCN(aq) + H₂O(l) ⇌ H₃O⁺(aq) + CN⁻(aq)
Ka = [H₃O⁺][CN⁻] / [HCN]
One of the conjugate acid-base pairs in a buffer solution is NH₄⁺ / NH₃. The Ka for NH₄⁺ is 5.6 × 10⁻¹⁰. What is the pH of a buffer prepared by mixing 0.25 M NH₄⁺ and 0.40 M NH₃?
NH₄⁺ + H₂O ⇌ NH₃ + H₃O⁺
Ka = [NH₃][H₃O⁺] / [NH₄⁺]
[H₃O⁺] = Ka × [NH₄⁺] / [NH₃]
The hydroxide ion concentration of a solution is 2.5 × 10⁻⁵ M. What is the hydronium ion concentration, [H₃O⁺]?
[H₃O⁺] = (1.0 × 10⁻¹⁴) / (2.5 × 10⁻⁵)
= 4.0 × 10⁻¹⁰ M
126C -> 42He + __
84Be Alpha Ray
NH₃ / NH₄Cl
Yes, because NH₃ is a weak base and NH₄⁺ is its common ion.
CH₃COOH(aq) + H₂O(l) ⇌ H₃O⁺(aq) + CH₃COO⁻(aq)
Ka = [H₃O⁺][CH₃COO⁻] / [CH₃COOH]
A buffer contains HC₂H₃O₂ / C₂H₃O₂⁻. The Ka for acetic acid is 1.8 × 10⁻⁵. What is the pH of a solution prepared from 0.15 M HC₂H₃O₂ and 0.45 M C₂H₃O₂⁻?
HC₂H₃O₂ + H₂O ⇌ C₂H₃O₂⁻ + H₃O⁺
Ka = [C₂H₃O₂⁻][H₃O⁺] / [HC₂H₃O₂]
[H₃O⁺] = Ka × [HC₂H₃O₂] / [C₂H₃O₂⁻]
A solution has a hydronium ion concentration of 4.0 × 10⁻³ M. Calculate the hydroxide ion concentration, [OH⁻].
[OH⁻] = (1.0 × 10⁻¹⁴) / (4.0 × 10⁻³)
= 2.5 × 10⁻¹² M
126C -> 127N + __
0-1e Beta Radiation
H₂CO₃ / NaHCO₃
Yes, because H₂CO₃ is a weak acid and they share a common ion.
NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH⁻(aq)
Kb = [NH₄⁺][OH⁻] / [NH₃]
The conjugate pair HCN / CN⁻ forms a buffer system. HCN has a Ka of 4.9 × 10⁻¹⁰. Calculate the pH when 0.30 M HCN and 0.10 M CN⁻ are mixed.
HCN + H₂O ⇌ CN⁻ + H₃O⁺
Ka = [CN⁻][H₃O⁺] / [HCN]
[H₃O⁺] = Ka × [HCN] / [CN⁻]
The concentration of OH⁻ in a sample of water is 8.0 × 10⁻⁹ M. Determine the concentration of H₃O⁺.
[H₃O⁺] = (1.0 × 10⁻¹⁴) / (8.0 × 10⁻⁹)
= 1.25 × 10⁻⁶ M
2713Al + 42He -> 3015P +__
10n n-emission
KOH / KCl
Not a buffer because KOH is a strong base.
H₂CO₃(aq) + H₂O(l) ⇌ H₃O⁺(aq) + HCO₃⁻(aq)
Ka = [H₃O⁺][HCO₃⁻] / [H₂CO₃]
A buffer is prepared using HCOOH / HCOO⁻. Formic acid has a Ka of 1.8 × 10⁻⁴. Find the pH of a solution containing 0.20 M HCOOH and 0.60 M HCOO⁻.
HCOOH + H₂O ⇌ HCOO⁻ + H₃O⁺
Ka = [HCOO⁻][H₃O⁺] / [HCOOH]
[H₃O⁺] = Ka × [HCOOH] / [HCOO⁻]
If the hydronium ion concentration in a solution is 7.5 × 10⁻¹¹ M, what is the hydroxide ion concentration?
[OH⁻] = (1.0 × 10⁻¹⁴) / (7.5 × 10⁻¹¹)
= 1.33 × 10⁻⁴ M
126C -> 127N + __
0-1e Beta Radiation
HCN / NaCN
Yes, because HCN is a weak acid and CN⁻ is the common ion.
C₅H₅N(aq) + H₂O(l) ⇌ C₅H₅NH⁺(aq) + OH⁻(aq)
Kb = [C₅H₅NH⁺][OH⁻] / [C₅H₅N]
A buffer system contains HF / F⁻. HF has a Ka of 6.8 × 10⁻⁴. What is the pH of a mixture containing 0.40 M HF and 0.20 M F⁻?
HF + H₂O ⇌ F⁻ + H₃O⁺
Ka = [F⁻][H₃O⁺] / [HF]
[H₃O⁺] = Ka × [HF] / [F⁻]
A basic solution has an OH⁻ concentration of 3.2 × 10⁻² M. Find the H₃O⁺ concentration.
[H₃O⁺] = (1.0 × 10⁻¹⁴) / (3.2 × 10⁻²)
= 3.125 × 10⁻¹³ M
99m43Tc -> 00Y + __
9943Tc Gamma radiation