Science
1,125 science calculators for chemistry, physics, biology, astronomy and the Earth sciences. Each one states the relation it uses and the units it expects, so class problems, lab work and quick checks come out right, free in your browser.
Empirical formula calculator
Type each element's amount and get the simplest whole-number formula: 40 % carbon, 6.7 % hydrogen and 53.3 % oxygen give CH2O.
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Empirical formula from masses calculator
Turn weighed element masses and the atomic masses from your worksheet into an empirical formula: 40 g of carbon, 6.7 g of hydrogen and 53.3 g of oxygen give…
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Reaction heat for amount calculator
Scale a molar reaction enthalpy to the amount that really reacts: 2 mol at −92.2 kJ/mol give a heat of −184.4 kJ, labelled exothermic because the system…
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Enthalpy scaled by coefficients calculator
Rescale the enthalpy of a thermochemical equation when you multiply its coefficients: doubling a step of −92.2 kJ gives −184.4 kJ, still exothermic.
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Heat of combustion per gram calculator
Turn a molar heat of combustion into energy per gram of fuel: methane at −890 kJ/mol and 16.04 g/mol releases about 55.5 kJ per gram.
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Enthalpy of dilution calculator
Turn a calorimetry reading into a molar enthalpy of dilution: −8.4 kJ measured while diluting 0.2 mol of solute gives −42 kJ/mol, an exothermic dilution.
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Enthalpy from heats of formation calculator
Get a reaction enthalpy straight from a formation table: burning methane, with −393.5 kJ/mol for carbon dioxide, −285.8 for water and −74.8 for methane, gives…
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Enthalpy from internal energy calculator
Turn a bomb-calorimeter ΔU into the ΔH that constant-pressure tables use: with ΔU of −1000 J, 1.5 fewer moles of gas and 298.15 K, ΔH ends up well below ΔU.
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Enthalpy of fusion calculator
Get the molar enthalpy of fusion from a melting measurement: 2 mol of ice absorbing 12.02 kJ give 6.01 kJ/mol, in line with tabulated values for water.
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Enthalpy of vaporization calculator
Get a liquid's molar enthalpy of vaporization from the heat it absorbed and the moles that turned to vapor: 40.7 kJ for 1 mol of water near 100 °C gives 40.7…
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Enthalpy of reaction calculator
Find whether a reaction releases or absorbs heat from formation enthalpies: methane burning in oxygen to carbon dioxide (−393.5 kJ/mol) and two moles of water…
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Reaction entropy change calculator
See how much a reaction changes disorder: making ammonia from N2 at 191.6, three H2 at 130.7 and two NH3 at 192.8 J/(mol·K) gives −198.1 J/(mol·K), an entropy…
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Equilibrium constant calculator
Get Kc straight from equilibrium concentrations: two reactants at 0.5 mol/L and one product at 2 mol/L, all with coefficient 1, give Kc 8.
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Equilibrium constant from cell potential
See how a cell voltage fixes an equilibrium constant: a Daniell cell at 1.1 V with 2 electrons at 298.15 K has K of about 10³⁷.
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Equilibrium partial pressure from Kp calculator
Give Kp, the starting pressure of pure A and the coefficients, and get every partial pressure at equilibrium: for A ⇌ B + C with a Kp of 0.25 and 1 atm of A…
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Equivalent weight calculator
Get the equivalent weight from molar mass and n-factor in one step: sulfuric acid at 98.079 g/mol with both protons reacting gives 49.0395 g per equivalent.
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Excess reactant remaining calculator
Find how much of the excess reactant is left over: 28 g of nitrogen and 10 g of hydrogen making ammonia use up all the nitrogen and leave 4 g of hydrogen…
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Faraday electrolysis mass calculator
Estimate how much metal plates out: 2.5 A for 3600 seconds in a copper bath, at 63.546 g/mol with two electrons per ion, deposits just under 3 g of copper.
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Final temperature of mixture calculator
Find the final temperature two bodies share: 100 g of water at 20 °C and 50 g of metal at 80 °C settle just a few degrees above 20 °C, because the water's heat…
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First-order half-life calculator
Turn a first-order rate constant into a half-life: with k of 0.1 per second, half the reactant is gone after just under 7 seconds, whatever the starting…
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Formal charge calculator
Find the formal charge of any atom in a Lewis structure from three counts: nitrogen in ammonium, with 5 valence electrons, no lone-pair electrons and 8 bonding…
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Fraction dissociated calculator
Find how much of a weak acid has ionized: an acid with a Ka of 0.000018 at 0.1 mol/L is just over 1% dissociated, solved exactly from Ostwald's law, with the…
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Freezing mixture temperature calculator
Find the temperature of an ice-salt mixture: a salt molality of 1.5 mol/kg in water, with a cryoscopic constant of 1.86, lowers the freezing point by 2.79 °C…
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Freezing point depression calculator
Work out the freezing-point drop for any solution: one mole of sodium chloride per kilogram of water, counted as two particles with a constant of 1.86, lowers…
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Gas collected over water calculator
Correct a wet-gas reading for water vapor: 750 torr total with 23.8 torr of water vapor leaves 726.2 torr of dry gas, ready for the ideal gas law.
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Gas density at STP calculator
Get a gas's density at standard conditions from its molar mass alone: dry air at 28.97 g/mol comes to about 1.3 kg/m³ at 0 °C and 1 atm, the same figure in…
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Ideal gas density calculator
Find how dense a gas is at the conditions you actually have: dry air at 101325 Pa and 298.15 K, with a molar mass of 0.02897 kg/mol, comes to about 1.2 kg/m³.
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Gas moles calculator
Count the moles of gas in a vessel: 101325 Pa in 0.022414 m³ at 273.15 K is almost exactly one mole, the classic textbook case at 0 °C and standard pressure.
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Gas pressure from moles calculator
Find the pressure inside a sealed vessel: 1 mol of gas in 0.024465 m³ at 298.15 K presses at about one atmosphere, or 101326.6719622604 Pa.
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Electrolysis gas volume calculator
Passing 96485.3321 coulombs with two electrons per molecule releases 0.5 mol of gas, or 11.2 litres at STP.
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Gas volume from moles calculator
One mole at 101325 Pa and 273.15 K takes up 0.022413969545 m³, straight from V = nRT/P. Give the moles, pressure and absolute temperature, keep the SI gas…
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Gay-Lussac final pressure calculator
A sealed sample at 1 atm heated from 300 K to 600 K reaches 2 atm, because pressure rises in step with absolute temperature.
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Gay-Lussac's law calculator
If a gas at 300 K in a rigid container goes from 1 atm to 2 atm, its temperature reaches 600 K. Enter the starting pressure, the starting temperature in kelvin…
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Spontaneity crossover temperature
Melting ice, with ΔH of 6.01 kJ/mol and ΔS of 0.022 kJ/(mol·K), crosses ΔG of zero near 273 K. Enter both changes to get that temperature in kelvin and Celsius…
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Gibbs free energy calculator
With ΔH of −100 kJ/mol, ΔS of −0.2 kJ/(mol·K) and 298.15 K, ΔG is −40.37 kJ/mol, so the reaction is spontaneous.
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Gibbs energy from equilibrium constant calculator
An equilibrium constant of 15000 at 298.15 K gives ΔG° of −23.8371685897 kJ/mol, so products are favoured.
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Non-standard Gibbs free energy calculator
A reaction with ΔG° of −30 kJ/mol and a reaction quotient of 0.1 at 298.15 K has an actual ΔG of −35.70800950243 kJ/mol.
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Reaction spontaneity calculator
A reaction with ΔH of −100 kJ/mol and ΔS of −50 J/(mol·K) at 298.15 K has ΔG of −85.0925 kJ/mol, so it is spontaneous.
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Graham's law calculator
Hydrogen at 2 g/mol effuses four times as fast as oxygen at 32 g/mol, because rates scale with one over the square root of molar mass.
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Graham effusion time calculator
If a gas of 4 g/mol takes 10 seconds to effuse, a gas of 16 g/mol takes 20 seconds under the same conditions.
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Unknown molar mass from effusion calculator
If helium at 4 g/mol effuses twice as fast as your unknown gas, the unknown has a molar mass of 16 g/mol.
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Grams to moles calculator
36.03 grams of water at 18.015 g/mol is exactly 2 moles: the amount of substance is the mass divided by the molar mass.
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Grams to particles calculator
18.015 grams of water at 18.015 g/mol is one mole, or 6.02214076 × 10²³ molecules. Enter a mass and a molar mass to get the moles and the particle count…
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Half-life calculator
Start with 100 units and a half-life of 10: after 20 time units, 25 remain and 75 have decayed. Enter the initial amount, the half-life and the elapsed time in…
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Number of half-lives calculator
20 hours with a 10-hour half-life is exactly 2 half-lives, which leaves 25 % of the start. Enter the elapsed time and the half-life in one unit to get the…
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Molar heat capacity ratio calculator
Air-like values of Cp 29.1 and Cv 20.8 J/(mol·K) give a ratio γ of 1.399038461538. Enter the two molar heat capacities in one unit to get the adiabatic index…
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Heat of neutralization calculator
A run that releases −57.3 kJ while forming 1 mole of water has a molar heat of neutralization of −57.3 kJ/mol.
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Heat of solution calculator
Dissolving 0.1 mol of solute that releases −4.2 kJ gives a molar heat of solution of −42 kJ/mol, an exothermic process.
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Heat required to raise temperature calculator
Raising 1 kg of water with a specific heat of 4184 J/(kg·K) by 1 kelvin takes 4184 joules. Enter mass, specific heat and temperature change to get the heat…
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Henderson–Hasselbalch calculator
A buffer with a pKa of 4.76 and equal amounts of conjugate base and acid, 0.1 each, has a pH of 4.76.
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Henry's law constant calculator
A dissolved gas concentration of 0.0012 mol/L under a partial pressure of 1 atm gives a Henry's law constant of 0.0012 mol/(L·atm).
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Henry's law gas solubility calculator
With a Henry constant of 0.0013 mol/(L·atm) and a partial pressure of 1 atm, the dissolved concentration is 0.0013 mol/L.
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Hess's law calculator
Double a step of −286 and reverse a step of −572, and the contributions of −572 and +572 cancel to an overall ΔH of 0.
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Hydrate formula calculator
Work out how many water molecules a hydrate holds: 24.96 g of hydrate that dries to 15.96 g of salt with a molar mass of 159.6 g/mol gives n of 5, written…
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Hydrogen ion from weak acid calculator
Get the real [H+] of a weak acid solution: 0.1 mol/L with a Ka of 0.000018 gives 0.001332670973 mol/L and a pH of 2.87527706155, from the exact quadratic rather…
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Hydroxide concentration from pOH calculator
Convert pOH straight into hydroxide concentration: a pOH of 7 gives 1 × 10⁻⁷ mol/L, the neutral point of pure water at 25 °C, and a pOH of 1 gives a tenth of a…
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Ideal gas law chemistry calculator
Enter any three of pressure, volume, moles and temperature and get the fourth from PV = nRT: 101325 Pa, 0.0224 m³ and 1 mol give 272.979758798406 K with the SI…
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Integrated rate law order checker
Decide the order of a reaction from your time and concentration readings: when ln[A] against time fits a perfect line with an R² of 1 and the plain…
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Internal energy change calculator
Apply the first law in one step: 500 J of heat absorbed while the system does 200 J of expansion work leaves an internal energy change of 300 J, with a note on…
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Ionic strength calculator
Sum up how charged a solution is: 0.1 mol/L of sodium chloride, entered as its two ions with charges +1 and −1, gives an ionic strength of 0.1 mol/L, and you…
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