Methodology & Sources
Every calculator on GenChemCalc is built from a stated formula and a documented set of constants. This page records where those formulas and values come from, so results can be checked.
How the calculators are derived
Each calculator implements a standard general-chemistry relationship and rearranges it for the quantity being solved. The formula used is shown on each calculator page and, where it helps, the worked steps are displayed alongside the answer. Inputs are converted to a consistent base unit (for example atm, litres and kelvin for the ideal gas law) before the calculation is performed.
Constants
Physical constants follow CODATA and NIST recommended values, expressed to the precision used in introductory chemistry courses. The values applied are:
- Avogadro's number, N_A = 6.022 × 10²³ mol⁻¹
- Ideal gas constant, R = 0.08206 L·atm·mol⁻¹·K⁻¹ (also 8.3145 J·mol⁻¹·K⁻¹)
- Faraday constant, F = 9.6485 × 10⁴ C·mol⁻¹
- Water ion product, Kw = 1.0 × 10⁻¹⁴ at 25 °C
- Standard temperature and pressure, 273.15 K and 1.000 atm
Atomic masses and reference tables
Atomic masses are taken from the periodic table and follow IUPAC standard atomic weights, rounded to the precision shown. Embedded reference data — standard enthalpies of formation, standard reduction potentials, specific heat capacities and solubility rules — match the reference section of the companion General Chemistry Workbook, which itself draws on standard tabulated values. Where a value is temperature dependent, the temperature is stated (most commonly 25 °C).
Unit conversions
Pressure conversions use 1 atm = 101.325 kPa = 760 mmHg = 760 Torr = 1.01325 bar. Volume conversions use 1 L = 1000 mL. Temperature is converted with T(K) = T(°C) + 273.15. Energy conversions use 1 cal = 4.184 J and 1 kJ = 1000 J.
Rounding and precision
Calculations are carried out at full floating-point precision and rounded only for display. Displayed results are not automatically limited to a fixed number of significant figures, because the correct number depends on the precision of your own measured inputs. The significant figures calculator can be used to round a result appropriately.
Accuracy and limitations
These tools assume idealised behaviour where the underlying model does: the ideal gas law assumes an ideal gas, strong-acid pH assumes complete dissociation, and so on. They are intended for learning and for checking your own working, not as a substitute for it. If a result does not match an expected answer, re-check the input units first. Errors can be reported through the contact details on the about page.