Chemistry Calculators cover three core lab arithmetic jobs: molar mass from a formula, solution concentration from mass and volume, and gas-state unknowns from PV = nRT. Each page shows substituted working, names the units in play, and keeps neighbouring topics on sibling URLs so one tool does not swallow another.
Choose a calculator by the question
Pick the page that matches the unknown. Formula on a bottle label needs molar mass. Grams and flask volume need molarity. Pressure, volume and temperature with an amount of gas need the ideal gas law. Opening the wrong tool still returns a number; the number will not answer the lab notebook question.
| Tool | Primary question | URL |
|---|---|---|
| Molecular Weight Calculator | What is the molar mass of this formula? | /chemistry-calculators/molecular-weight-calculator |
| Molarity Calculator | What concentration, mass or dilution volume is required? | /chemistry-calculators/molarity-calculator |
| Ideal Gas Law Calculator | What P, V, n or T closes PV = nRT? | /chemistry-calculators/ideal-gas-law-calculator |
A common prep path starts with molar mass, then feeds g/mol into the molarity mass equation. Gas stoichiometry often needs moles from PV = nRT first, then a mass from molar mass.
Molar mass before weighing
Standard atomic weights multiply by atom counts after brackets and hydrates expand. Water lands near 18.015 g/mol; CuSO4·5H2O near 249.68 g/mol; [Co(NH3)6]Cl3 near 267.48 g/mol. Those fixtures confirm parsing before any solid hits the balance. Percent composition sits on the same page so elemental mass fractions stay tied to the formula that produced them.
Ionic salts use formula mass with the same arithmetic. Naming debates between molecular weight and molar mass matter less than using grams per mole for the next weighing step.
Solutions and dilutions
Molarity is moles of solute per litre of solution. Mass for a target M equals M × V × molar mass. Dilutions follow C1V1 = C2V2 when only solvent is added. A teaching check is 500 mL of 0.1 M NaCl at 58.44 g/mol, which needs about 2.92 g.
Molality and normality are defined on the molarity page so they are not confused with M. Volumetric glassware volume, not solvent poured first, is the V that enters the formula.
Gases and absolute temperature
PV = nRT needs kelvin. Celsius 25 becomes 298.15 K. The litre-atmosphere constant used in worked examples is R = 0.082057 L·atm·K⁻¹·mol⁻¹. One mole at 1 atm and 273.15 K occupies about 22.4 L under that ideal model. Real gases near condensation or high pressure need compressibility checks the ideal page flags but does not replace.
How the chemistry pages stay separate
Molecular weight owns formula parsing and percent composition. Molarity owns solution prep and dilution algebra and links out for molar mass rather than re-teaching the periodic table. Ideal gas owns R selection, kelvin conversion and fixed-n combined-gas changes. Cross-links carry the reader; duplicated essays do not.
Limits stay explicit: conventional atomic weights, ideal-gas assumptions, and volumetric marks at stated temperature. Supplier certificates and course-specific STP definitions override site defaults when they disagree.
Related topics elsewhere on the site
Electrical tools and construction estimators live in other hubs on purpose. Resistor colour codes and voltage drop belong with electrical calculators. Room air-conditioner BTU sizing sits with construction tools and links to square footage rather than to ideal-gas temperature conversion.
Chemistry Calculators stay focused on molar mass, solution concentration and PV = nRT. Cross-links carry readers to neighbouring questions; duplicated essays do not.
Summary
Chemistry Calculators route formula mass, solution concentration and ideal-gas unknowns to three focused pages. Use molar mass to weigh, molarity to fill volumetric flasks, and PV = nRT when the state variables are the homework. Shared fixtures (water, hydrates, NaCl prep, R = 0.082057, 298.15 K) keep classroom checks aligned across the set.