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Chemistry calculators

Concentrations, pH, dilutions, gas laws and reaction yields: the maths behind the lab bench, with every constant and assumption stated.

Electronegativity CalculatorPauling-scale electronegativity of an element, or the difference between two elements to judge bond polarity.Molarity from massConcentration of a solution made from a known mass of solute.Solution dilution (C₁V₁ = C₂V₂)Stock volume and diluent needed to hit a target concentration.pH from hydrogen ion concentrationConversion between [H⁺] and pH, with pOH and [OH⁻] at 25 °C.Henderson–Hasselbalch (buffer pH)Buffer pH from the acid dissociation constant and the base/acid ratio.Percent yieldHow much product a reaction actually gave versus the theoretical maximum.Mass percent concentrationSolute mass as a percentage of total solution mass, plus ppm.Radioactive decay & half-lifeAmount of a substance remaining after a given elapsed time.Beer–Lambert law (absorbance)Absorbance and transmittance of a solution from its concentration.Osmotic pressure (van’t Hoff)Pressure needed to stop osmosis across a semipermeable membrane.Solubility Rules CalculatorPredicts whether an ionic compound is soluble in water, using the standard solubility rules.Mole CalculatorConverts between mass and moles of a substance using its molar mass.Types of Chemical Reactions ClassifierIdentifies the standard reaction type from the number of reactants and products.Ionic CalculatorThe correct chemical formula of an ionic compound from a chosen cation and anion, by balancing charges.Mole Ratio CalculatorMole ratio between two substances in a balanced reaction, from their equation coefficients or from given mole amounts.Net Ionic Equation CalculatorBalances a double-displacement reaction between two soluble ionic compounds and removes the spectator ions.Theoretical Yield CalculatorMaximum mass of product obtainable from a limiting reagent, using molar masses and the balanced equation ratio.Entropy of ReactionEntropy change of a reaction from the total entropy of its products and reactants.Water Boiling Point (Altitude)How the boiling point of water falls as elevation rises, from the drop in atmospheric pressure.Electron Configuration CalculatorFull electron configuration for any element from atomic number 1 to 56, following the Aufbau principle.Molality of a solutionMoles of solute per kilogram of solvent, a concentration measure independent of temperature.Acid-base titration (equivalence point)Unknown acid or base concentration from the titrant volume at the equivalence point.Freezing point depressionHow much a solvent’s freezing point drops when a solute is dissolved in it (a colligative property).Boiling point elevationHow much a solvent’s boiling point rises when a solute is dissolved in it (a colligative property).Buffer capacity (Van Slyke equation)How resistant a buffer solution is to pH change, from its total concentration and pKa.Arrhenius equationReaction rate constant at a given temperature from activation energy and pre-exponential factor.Mole fraction of a mixtureFraction of the total moles in a mixture contributed by each component.Water hardness (as CaCO₃)Total water hardness as calcium carbonate equivalent, from calcium and magnesium ions.Serial dilution seriesFinal concentration after a series of equal-factor dilutions, and the concentration at each step.Raoult’s law (vapor pressure of a solution)Vapor pressure of an ideal solution containing a non-volatile solute.Mol/L to mg/L CalculatorConverts molar concentration (mol/L) to mass concentration (mg/L) and back, using the molar mass of the substance.Weak acid/base pH from Ka or KbpH of a weak acid or base solution from its dissociation constant and starting concentration.Activation energy from two rate constantsActivation energy from rate constants at two temperatures (two-point Arrhenius equation).Kp ↔ Kc equilibrium constant conversionConvert between pressure-based and concentration-based equilibrium constants for a reaction.Degree of unsaturation (DBE)Number of rings and pi bonds in a molecule from its molecular formula.Empirical formula from mass percentSimplest whole-number atom ratio of a compound from percent composition and atomic masses.Ionic strength of a solutionIonic strength from the concentration and charge of every ion present in a solution.Graham's law of effusion/diffusionRelative rate at which two gases effuse or diffuse, from their molar masses.Radioactive activity (Bq / Ci)Decay rate of a radioactive sample from its amount and half-life, in becquerels and curies.Rate constant from concentration vs. timeReaction rate constant k from concentration data, for zero, first or second order kinetics.Atom economyShare of reactant mass that ends up in the desired product versus all products formed.Average atomic mass from isotopesWeighted average atomic mass of an element from its isotope masses and natural abundances.Molecular Weight CalculatorMolecular weight of a chemical formula, summing standard atomic weights for each element present.Nernst Equation CalculatorCell potential under non-standard conditions from standard potential, temperature, electrons transferred and the reaction quotient.Gibbs free energyReaction spontaneity from the change in enthalpy, entropy and temperature.Partial pressure (Dalton's law)Partial pressure of each gas in a mixture from its moles, volume and temperature.Bond order (MO theory)Bond order and bond stability of a molecule from its bonding and antibonding electron counts.Diffusion coefficient (Stokes-Einstein)Diffusion rate of a spherical particle in a fluid, from its size, viscosity and temperature.Young-Laplace pressure (capillary)Pressure difference across a curved liquid interface, from surface tension and curvature.Isoelectric point (pI)pH at which a molecule such as an amino acid carries no net electric charge.Grams to molesConverts a mass in grams to an amount in moles using the substance’s molar mass.Molar mass of a gasFinds a gas’s molar mass from its mass, pressure, volume and temperature (ideal gas law).Normality of a solutionConverts molarity to normality using the number of equivalents per mole.pKa from KaCalculates pKa from the acid dissociation constant Ka using pKa = -log10(Ka).Alligation mixing ratioFinds the ratio and volumes of two concentrations that mix to a target concentration.Crude protein from nitrogenEstimates crude protein percentage from measured nitrogen content and a conversion factor.PPM to molarityConverts a concentration in ppm (mg/L) to molarity using the solute molar mass.Reaction quotient (Q)Calculates the reaction quotient Q for aA + bB ⇌ cC + dD from current concentrations.Combustion analysisFinds the empirical formula of a CHO compound from the CO2 and H2O produced by combustion.Saponification valueDetermines a fat or oil’s saponification value from a KOH back-titration with HCl.Vapor pressure (Clausius–Clapeyron)Finds vapor pressure at a new temperature from a known point and enthalpy of vaporization.Avogadro's number (particles from moles)Number of particles and sample mass from an amount in moles.Atom composition (protons, neutrons, electrons)Subatomic particle counts from atomic number, mass number and charge.Percent ionic characterIonic character of a bond estimated from the electronegativity difference.Lattice energy (Kapustinskii equation)Ionic crystal lattice energy from ion charges, radii and formula-unit count.Cubic unit cell (packing efficiency)Edge length, atoms per cell and packing efficiency for SC, BCC and FCC lattices.Miller indices from axial interceptsMiller indices (hkl) of a crystal plane, plus interplanar spacing for a cubic lattice.Combustion reaction balancerBalanced coefficients for complete combustion of a CxHyOz compound in oxygen.Stoichiometric air-fuel ratioTheoretical air-to-fuel mass ratio for complete combustion of a CxHy hydrocarbon.STP conversionCorrects a measured gas volume to STP and finds the equivalent moles.Enzyme activity from absorbanceEnzyme activity in units (µmol substrate/min) from an absorbance-vs-time assay.Chemical oxygen demand (COD)COD of a water or wastewater sample from a ferrous ammonium sulfate (FAS) back-titration.Activity coefficient (Debye-Hückel)Ionic activity coefficient of a dissolved ion from its charge and the solution ionic strength.Gibbs' phase ruleDegrees of freedom of a chemical system from its number of components and coexisting phases.Bleach dilution to target strengthBleach and water needed to dilute a stock solution down to a target free-chlorine strength.Percent solution (% w/v)Weight-per-volume percent concentration of a solution from the mass of solute dissolved.Radiocarbon (carbon-14) datingEstimated age of an organic sample from the fraction of carbon-14 remaining.Rate constant from a rate lawReaction rate constant k from a single measured rate and reactant concentrations.Electrolysis mass deposited (Faraday's law)Mass of an element deposited or liberated during electrolysis, from current and time.Resuspension volume/concentrationBuffer volume to resuspend a dried sample to a target concentration, or vice versa.

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