Chemistry in CALCULA
The Chemistry field covers solutions (concentration, dilution), acids and bases, equilibria, kinetics and thermochemistry.
Concentration and dilution
A weighed mass becomes an amount of substance (moles) through the molar mass, then a concentration by dividing by the volume. Diluting conserves the amount of solute: the product concentration × volume stays constant.
Example
To prepare 250 mL of 0.1 mol/L salt solution from a 1 mol/L stock, take 25 mL of stock and make it up to 250 mL.
pH and equilibria
pH measures acidity on a logarithmic scale: one pH unit is a factor of 10 on the H₃O⁺ concentration. A solution at pH 3 is ten times more acidic than one at pH 4.
Kinetics and thermochemistry
The Arrhenius law links a reaction's rate to temperature and activation energy: raising the temperature speeds it up sharply. The sign of the Gibbs free energy ΔG tells whether a transformation is spontaneous (ΔG < 0).
Example
A reaction whose rate doubles every 10 °C (a rule of thumb) is about 8 times faster at 60 °C than at 30 °C.
Typing it into CALCULA
Choose the sub-field in the “≡” menu, then fill in molar mass, volume, concentration or temperature depending on the calculation. Radiometric dating has its own guide.