Comprehensive Chemistry Key Concepts: Moles, pKa, Buffer, and Coulomb’s Law

Moles

10^3 mmol = 10^6 micromol = 10^9 nmol

Moles calculation

Moles = mass (g)/molar mass (g/mol)

Molar concentration

mol/L

Millimolar concentration

mmol/L

Micromolar concentration

micromol/L

Concentration unit

M

Absorbance unit

unitless

Wavelength unit

nm

Enzyme activity unit

micromol/min or units

Ka

Acid dissociation constant; measures strength of acid

pKa

-log(Ka)

pKa relationship

Smaller pKa = stronger acid

Acid-base equilibrium equation

pH=pKa + log([A-]/[HA])

Half-equivalence point

[HA] = [A-] when pH = pKa

Dilution factor (DF)

DF = total volume/sample volume

P20 pipettor

2-20 microliters

P200 pipettor

20-200 microliters

P1000 pipettor

100-1000 microliters

Isoelectric point (pI)

pI = (pKa1 + pKa2) / 2 for neutral amino acids

Buffer components

Weak acid + conjugate base

Henderson-hasselbalch equation

pH = pKa + log([A-]/[HA])

Weak acid equilibrium

Ka = ([H+][A-]) / [HA]

Weak base equilibrium

Kb = ([BH+][OH-]) / [B]

Percentage saturation equation

X (g) = 51.5 (S2-S1) / (100% - 0.3S2)

Coulomb's Law

Force (F) = (q1 q2) / (D r^2)