Chemistry Calculators: Molarity, Dilution, Buffers, Absorbance & pH
Choose calculators for molarity, stock dilution, Henderson-Hasselbalch buffer preparation, Beer-Lambert absorbance, recrystallization solubility, and pH.
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| Goal and tool | Required inputs | How to check |
|---|---|---|
| Molarity (mol/L) from moles or reagent mass → | Moles or mass (g), molar mass and total solution volume | Convert mL to L and use final solution volume |
| Required stock volume V₁ and dilution factor (C₁V₁=C₂V₂) → | Stock concentration C₁, target C₂ and final volume V₂ | Verify C₂ < C₁ and added solvent ≈ V₂ − V₁ |
| Henderson-Hasselbalch buffer pH, recipe & acid/base titration → | pKa, weak acid [HA], conjugate base [A⁻], total molarity & volume | Check mole ratio n_b/n_a and effective buffer range (pKa ± 1) |
| Beer-Lambert absorbance A = εcℓ, transmittance & calibration → | Absorbance A, molar absorptivity ε, path length ℓ or standards | Check T = 10⁻ᴬ and linear absorbance range (A ≈ 0.1–1.0) |
| Recrystallization yield from cooling or water evaporation → | Hot solubility S₁, cold solubility S₂, solution or water mass | Check (100 + S₁) saturated ratio and anhydrous crystal basis |
| pH, pOH and [H⁺] for strong and weak acids/bases → | Molarity C, degree of ionization α or Ka at 25 °C | Verify pH = −log₁₀[H⁺] and pH + pOH = 14 at 25 °C |
Verify whether volume refers to total solution or solvent water. Check buffer capacity bounds (pKa ± 1), Beer-Lambert linear absorbance range, and anhydrous vs. hydrate recrystallization.
14 calculators
Moles & Molarity
Calculate molarity from moles and solution volume, or convert mass to moles with a supplied molar mass. View results in mol/L and mmol/L.
Dilution Calculator
Find the required stock volume from stock concentration, target concentration and final solution volume using C₁V₁ = C₂V₂.
pH Calculator
Compute pH from hydrogen ion concentration or the reverse, in both directions. Accepts e-notation like 1e-7 and shows the substituted pH = −log₁₀[H⁺] working plus an acidic / neutral / basic classification based on 25 °C water.
Solubility & Recrystallization Calculator
From the solubility per 100 g of water, compute the maximum dissolved amount, the composition of a saturated solution, and the crystals precipitated on cooling or evaporation — with the mass-balance steps shown.
Acid-Base Titration Calculator
Work through acid-base titration calculations with the mole working shown: find an unknown concentration, the volume needed for neutralization, or the original concentration after dilution. Enter the acid and base valences directly.
Redox Titration Calculator
Work through redox titration calculations with the electron moles shown: find an unknown concentration, the volume needed for the reaction, or the result of an indirect iodine titration with thiosulfate. Pick a substance and the electron count is filled in from its half-reaction.
Bond Energy & Reaction Enthalpy Calculator
Work out the reaction enthalpy ΔH from average bond energies. Pick the bonds broken and formed from a table, enter the counts, and see the totals, the subtraction and whether the reaction is exothermic or endothermic. A reverse mode finds an unknown bond energy from ΔH.
Ideal Gas Law Calculator
Solve PV = nRT for pressure, volume, amount or temperature with unit conversions (Pa, kPa, atm, mmHg, L, mL, °C, K) and the working shown. The combined gas law P₁V₁/T₁ = P₂V₂/T₂ and gas density or molar mass with ρ = PM/(RT) are supported too.
Mass Percent Concentration Calculator
Work out mass percent concentration from solute, solvent and solution masses, find the solute and water needed for a target solution, mix or evaporate solutions, and convert between mass percent and molarity using density and molar mass — all with the working shown.
Beer-Lambert Law, Absorbance & Calibration Calculator
Solve the Beer-Lambert Law (A = εcℓ) for absorbance, molar concentration, molar absorptivity, or path length. Includes dilution factor (DF) and mass concentration (mg/L) conversions, absorbance A ⇄ percent transmittance %T, and least-squares calibration curve fitting for unknown sample quantification.
Buffer Solution & Henderson-Hasselbalch Calculator
Calculate conjugate acid-base buffer recipes using the Henderson-Hasselbalch equation (pH = pKa + log([A⁻]/[HA])). Solves mass in grams for diverse hydrates, 1 M HCl/NaOH titration volumes, Good buffer temperature corrections (4°C, 25°C, 37°C), and Van Slyke buffer capacity β.
Osmotic Pressure & Van 't Hoff Calculator
Calculate osmotic pressure (kPa, atm, mmHg), molarity, temperature, and van 't Hoff factor i using Π = iCRT. Simulates physiological saline / glucose RBC tonicity (hemolysis vs. crenation) and macromolecular molar mass determination by membrane osmometry.
Electrochemistry, Nernst Equation & Faraday's Law Calculator
Calculate electrolysis mass, current, time, valence z, and STP gas volume via Faraday's Law (Q = It, m = MIt/(zF)), solve non-standard cell potentials and concentration cells with the Nernst equation (E = E° − (RT/nF)ln Q), and determine standard cell EMF E°cell, Gibbs free energy ΔG° = −nFE°, and equilibrium constant K with a 1-click toggle between textbook F = 96,500 C/mol and exact CODATA F = 96,485.33212 C/mol.
Arrhenius Equation, Activation Energy & Reaction Rate Calculator
Solve the two-temperature Arrhenius equation (ln(k₂/k₁) = −(Ea/R)(1/T₂ − 1/T₁)) for activation energy Ea, rate constant k₂, or target temperature T₂, fit multi-point OLS Arrhenius plots (ln k vs. 1/T) with Eyring transition-state parameters (ΔH‡, ΔS‡, ΔG‡), and calculate 0th-, 1st-, and 2nd-order integrated rate laws (half-life t₁/₂, shelf-life t₉₀) with a 1-click toggle between exact CODATA R = 8.3144626 J/(mol·K) and textbook R = 8.31 J/(mol·K).
Worked examples and guides
scienceArrhenius Equation & Activation Energy Guide: 2-Temp Solving, Plots & Half-Lives
Master the Arrhenius equation k = A·exp(−Ea/RT): avoid kJ vs J and °C vs K traps, run multi-point OLS Arrhenius plots with Eyring parameters (ΔH‡, ΔS‡), compare CODATA vs textbook R, and solve 0th-, 1st-, and 2nd-order half-lives and shelf-life t90.
GuideGuide to Faraday's Law of Electrolysis, Nernst Equation & Cell Potential: Formulas & Worked Examples
Master electrochemistry calculations from Faraday's law of electrolysis (Q = It, m = MIt/zF, STP gas volume) to the Nernst equation (E = E° − (RT/nF)ln Q), concentration cells, standard cell EMF E°cell, Gibbs free energy ΔG° = −nFE°, and equilibrium constant K with step-by-step worked examples.
GuideGuide to Osmotic Pressure & Van ’t Hoff’s Law: Formulas, Tonicity, and Molar Mass
Master osmotic pressure calculations using van ’t Hoff’s law (Π = iCRT). Covers electrolyte dissociation factor i, physiological saline (0.90% NaCl) and glucose tonicity evaluation (RBC hemolysis vs. crenation), and polymer molar mass determination via membrane osmometry with worked examples.
GuideMolarity & Dilution Calculation Guide: C=n/V, C₁V₁=C₂V₂, Mass % Conversion & Hydrates
Calculate molarity C=n/V and stock dilutions C₁V₁=C₂V₂ with step-by-step examples, convert mass percent and density via C=10ρw/M, and compare anhydrous vs. hydrate reagent masses.
GuideHow to Calculate pH: [H⁺], pOH, Weak-Acid 5% Rule & Ultra-Dilute Limits
Master pH and pOH calculations across all conditions: strong vs. weak acids (5% ionization rule vs. quadratic formula), water autoionization in 10⁻⁸ M ultra-dilute solutions, temperature-dependent pKw, and logarithmic significant figures.
GuideHow to Calculate Crystals Precipitated on Cooling
Find the mass of crystals that precipitate when a saturated solution is cooled: dissolved while hot, still soluble when cold, and the difference.
GuideBuffer Solution Preparation & Henderson-Hasselbalch Guide: Hydrates, Titration & Temperature Shifts
Master conjugate acid-base buffer preparation using the Henderson-Hasselbalch equation (pH = pKa + log([A⁻]/[HA])). Step-by-step calculations for monobasic/dibasic sodium phosphate hydrate mass discrepancies, Tris base 1 M HCl titration volumes, 4°C cold-room pKa shifts (ΔpKa/ΔT), Van Slyke buffer capacity β, and acid-resistance simulations.
GuideBeer-Lambert Law & Absorbance Calculations: %T, Dilution & Calibration Curves
Step-by-step guide to solving the Beer-Lambert Law (A = εcℓ) for absorbance, molar concentration, molar absorptivity, and path length. Covers μmol/L and 1 mm cuvette conversions, dilution factor (DF) and mg/L calculations, %T and dark-signal correction, linear calibration curves, and stray-light limits.
GuideIdeal Gas Law vs Combined Gas Law: When to Use Each
Choose between PV = nRT and P₁V₁/T₁ = P₂V₂/T₂ by checking whether the amount of gas changes. Includes unit conversion (C to K, mL to L, mmHg to Pa), the 22.4 L molar volume at STP, gas density and molar mass, common mistakes, and a free calculator for checking answers.
GuideHow to Solve Redox Titration Calculations
Redox titrations balance electron moles, not H⁺ and OH⁻. Electron counts from half-reactions, worked examples for permanganate and iodometry, and common mistakes.
GuideHow to Calculate Mass Percent Concentration
Mass percent = solute mass ÷ solution mass × 100. Learn why 20 g of salt in 100 g of water is about 16.7% and not 20%, how to prepare 200 g of 8% brine, how mixing and evaporation change the concentration, and how to convert between mass percent and molarity, with a free calculator for checking.
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