pKa to Ka Conversion Calculator – pka to ka Converter
pKa to Ka Calculator
We use this pKa to Ka calculator with Ka = 10^(-pKa) formula to convert the negative logarithm of the acid dissociation constant (pKa) and the acid dissociation constant (Ka) itself.
Let’s say we have an acid with a pKa value of 4.7. To find its Ka value, we would use a pKa to Ka Calculator. The calculator would perform the following conversion:
Ka = 10^(-pKa) Ka = 10^(-4.7) Ka ≈ 1.995 × 10^-5This result tells us that the acid has a Ka of approximately 1.995 × 10^-5, indicating it’s a weak acid. The calculator simplifies this process, especially for more complex pKa values that might be challenging to compute manually.
pKa to Ka Conversion Chart
| Acid | pKa converted to | Ka |
|---|---|---|
| Hydrochloric Acid | -7.0 | 1.0 × 10^7 |
| Sulfuric Acid | -3.0 | 1.0 × 10^3 |
| Nitric Acid | -1.4 | 2.51 × 10^1 |
| Hydrofluoric Acid | 3.17 | 6.76 × 10^-4 |
| Acetic Acid | 4.76 | 1.74 × 10^-5 |
| Carbonic Acid | 6.35 | 4.47 × 10^-7 |
| Ammonium Ion | 9.25 | 5.62 × 10^-10 |
| Water | 14.0 | 1.0 × 10^-14 |
| Ethanol | 15.9 | 1.26 × 10^-16 |
| Ammonia | 38.0 | 1.0 × 10^-38 |
pKa to Ka Formula
The formula for converting pKa to Ka is:
pKa = -log10(Ka)This formula is derived from the definition of pKa, which is the negative logarithm (base 10) of Ka.
Imagine we have an acid with a pKa of 5.8 and want to find its Ka value.
Ka = 10^(-5.8) Ka ≈ 1.585 × 10^-6This calculation shows that an acid with a pKa of 5.8 has a Ka of approximately 1.585 × 10^-6. This relatively low Ka value indicates that the acid is weak, as it doesn’t dissociate readily in solution.
How To Convert pKa to Ka
To convert from pKa to Ka, we use: Ka = 10^(-pKa)
- Identify the pKa value of your acid.
- Apply the conversion formula: Ka = 10^(-pKa).
- Express the result in scientific notation.
Converting a pKa of 5.5:
- Take pKa = 5.5
- Ka = 10^(-5.5)
- Ka = 3.16 × 10^(-6)
Formic Acid
pKa = 3.75
Ka = 10^(-3.75)
Ka = 1.78 × 10^(-4)Benzoic Acid
pKa = 4.20
Ka = 10^(-4.20)
Ka = 6.31 × 10^(-5)Hydrofluoric Acid
pKa = 3.17
Ka = 10^(-3.17)
Ka = 6.76 × 10^(-4)Lactic Acid
pKa = 3.86
Ka = 10^(-3.86)
Ka = 1.38 × 10^(-4) Phenol
pKa = 9.95
Ka = 10^(-9.95)
Ka = 1.12 × 10^(-10)Relationship Between pH, pKa, and Ka
They are connected through the Henderson-Hasselbalch equation:
pH = pKa + log([A⁻]/[HA])When pH = pKa:
- The concentrations of acid [HA] and conjugate base [A⁻] are equal.
- The solution is at its buffer capacity maximum.
- The ratio [A⁻]/[HA] = 1.
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