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Calculate solution molarity (mol/L), moles of solute, required volume, or solve dilution problems with M₁V₁ = M₂V₂. The most essential concentration calculator for chemistry labs.
Molarity (M) = moles per liter of solution. A 1 M NaCl solution contains 58.44 g/L. Molarity directly connects to reacting particle counts — making all stoichiometric and dilution calculations straightforward.
| Unit | Definition | Field |
|---|---|---|
| Molarity (M) | mol/L | Chemistry labs |
| mM | mmol/L | Biochemistry |
| ppm (mg/L) | mg per liter | Environmental |
| % w/v | g/100mL | Pharmacy |
| mg/mL | = g/L | Biology |
500 mL of 0.1 M NaCl: mol = 0.1×0.5 = 0.05 mol. Mass = 0.05×58.44 = 2.922 g. Weigh 2.922 g, dissolve, dilute to 500 mL in volumetric flask.
M₁V₁ = M₂V₂. Make 1 L of 0.5 M HCl from 12 M stock: V₁ = (0.5×1000)/12 = 41.7 mL. Add to ~900 mL water, dilute to 1 L. Always add acid to water.
Blood glucose: 70-100 mg/dL = 3.9-5.6 mM. IV saline: 0.9% NaCl = 0.154 M = 308 mOsm/L.
Molarity is the universal language of solution chemistry. Whether you are preparing a buffer for cell culture, standardizing a titrant, or calculating drug plasma levels, molarity is the concentration unit that makes stoichiometric calculations direct and straightforward.
To prepare any molar solution: first calculate the mass required (mass = molarity × volume × molar mass), weigh the solute accurately on an analytical balance, dissolve in approximately 80% of the final volume, transfer to a volumetric flask, and dilute precisely to the calibration mark. Never use a beaker to prepare a standard solution — volumetric flasks are calibrated to ±0.02-0.05% accuracy while beakers have only ±5% accuracy.
Clinical laboratories report blood chemistry in multiple concentration units. Blood glucose: 70-100 mg/dL = 3.9-5.6 mM (divide mg/dL by 18.016 for glucose). Serum sodium: 136-145 mEq/L = 136-145 mM (sodium is monovalent so mEq = mmol). Creatinine: 0.6-1.2 mg/dL = 53-106 μM. Understanding unit conversions between mg/dL, mM, mEq/L, and μM is essential for clinical interpretation.
Most biological buffers are prepared as concentrated stock solutions and then diluted. A 10× PBS stock at 1.37 M NaCl is diluted 1:10 to give 1× PBS at 0.137 M NaCl. Stock solutions save time and ensure consistency across experiments. The dilution formula M₁V₁ = M₂V₂ is applied every time a stock is diluted — understanding this equation is essential for any laboratory scientist.
Molarity (M) is the number of moles of solute dissolved per liter of solution, expressed as mol/L. It is the most widely used concentration unit in chemistry because it directly relates to the number of reacting particles — making all stoichiometric calculations involving solutions straightforward and consistent. A 1 M solution of any substance contains exactly 6.022 × 10²³ solute particles per liter.
Understanding molarity is essential for every chemistry laboratory — from preparing buffer solutions for biochemistry experiments to standardizing titrant solutions for analytical chemistry to calculating drug plasma concentrations in pharmacology. It is the foundation of quantitative solution chemistry.
To prepare 500 mL of 0.250 M NaCl: Calculate moles needed: 0.250 mol/L × 0.500 L = 0.125 mol. Calculate mass: 0.125 mol × 58.44 g/mol = 7.305 g. Weigh 7.305 g NaCl precisely on an analytical balance. Dissolve in approximately 400 mL of distilled water in a 500 mL volumetric flask. Dilute to the 500 mL calibration mark exactly. Mix thoroughly. Always use volumetric glassware — not beakers — for accurate concentrations. Volumetric flasks are calibrated to ±0.02-0.05% accuracy.
The dilution equation M₁V₁ = M₂V₂ conserves moles of solute. Since moles = M × V, when you dilute a solution, moles before dilution = moles after dilution. Example: Prepare 1 L of 0.1 M HCl from 12 M concentrated HCl stock. V₁ = M₂V₂/M₁ = (0.1 × 1.0)/12 = 0.00833 L = 8.33 mL. Measure 8.33 mL of 12 M HCl. Add slowly to approximately 900 mL of distilled water in a 1 L volumetric flask (always add acid to water — never water to concentrated acid — the heat of dilution can cause dangerous spattering). Dilute to 1 L mark exactly.
Different scientific fields use different concentration units. Molarity (M, mol/L): universal in chemistry, temperature-dependent. Molality (m, mol/kg): temperature-independent, used for colligative properties. ppm (mg/L in dilute aqueous solutions): environmental monitoring, water quality. mg/mL (= g/L): biology, pharmacology, drug concentrations. % w/v (g/100 mL): pharmacy and food science. % w/w (g/100 g): industrial chemistry. mEq/L (milliequivalents per liter): clinical electrolytes. mOsm/L: osmolarity in physiology.
Clinical labs report blood chemistry in multiple units. Blood glucose: normal 70-100 mg/dL = 3.9-5.6 mM (divide mg/dL by 18.016 for glucose). Serum sodium: normal 136-145 mEq/L = 136-145 mM. Serum potassium: 3.5-5.0 mEq/L. Serum chloride: 96-106 mEq/L. Blood urea nitrogen (BUN): 7-20 mg/dL = 2.5-7.1 mM. Serum creatinine: 0.6-1.2 mg/dL = 53-106 μM. Understanding unit conversions prevents medical errors when reading laboratory reports.
Serial dilutions make very dilute solutions from concentrated stocks by repeated equal dilutions. A 1:10 serial dilution: take 1 mL, add 9 mL buffer → 10⁻¹ (10× less concentrated). Take 1 mL of that, add 9 mL → 10⁻² (100× less). After 6 serial 1:10 dilutions: 10⁻⁶ = 1/1,000,000 of original. Used in microbiology for colony counting (plating diluted cultures to count colonies), immunology for antibody titer determination, and pharmacology for dose-response curves. The final concentration = initial concentration × dilution factor.