Concentration, worked out in one place.
Find the molarity of any solution, the moles or grams of solute you need, and the exact recipe to prepare it. Solve for whichever piece you are missing and watch the numbers update as you type.
Your solution
What these numbers mean
How volume changes the concentration
Dilution curve at constant moles
Grams needed per target molarity
Concentration scorecard
Dilution helper (M1V1 = M2V2)
Figure out how much stock solution to take, and how much solvent to add, to reach a lower concentration.
Recipe for common target molarities
Solute needed to prepare each concentration at your current solution volume.
| Target molarity | In millimolar | Moles needed | Mass needed | vs your mix |
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Molarity, explained
What Is Molarity?
Molarity (M) is the number of moles of solute per liter of solution. It is the most common way to express concentration in chemistry. A 1 M solution contains 1 mole of solute in 1 liter of total solution.
How to Calculate Molarity
Molarity = moles of solute / volume of solution in liters. To find moles from mass, divide the mass in grams by the molar mass (g/mol) from the periodic table. Then divide by the volume to get molarity.
Molarity vs Molality
Molarity (M) uses liters of solution, while molality (m) uses kilograms of solvent. Molality does not change with temperature because mass is constant, while molarity changes as liquid volume expands or contracts with temperature.
Dilution Calculations
When diluting a solution, use M1V1 = M2V2. If you have 100 mL of 2 M solution and add water to make 500 mL, the new molarity is (2 x 0.1) / 0.5 = 0.4 M. This formula is essential for laboratory preparation.
Common questions
What is the difference between molarity and molality?
Molarity (M) is moles per liter of solution. Molality (m) is moles per kilogram of solvent. Molality is preferred for precise work because it does not change with temperature, while molarity does as the solution volume changes.
How do I convert mass to moles?
Divide the mass in grams by the molar mass of the substance. The molar mass is found on the periodic table. For example, NaCl has a molar mass of 58.44 g/mol, so 29.22 grams equals 0.5 moles.
What is a normal solution?
Normality (N) equals molarity multiplied by the number of equivalents. For acids, the number of equivalents is the number of ionizable hydrogens. A 1 M H2SO4 solution is 2 N because sulfuric acid has two ionizable hydrogens.
How is molarity used in the lab?
Molarity is used to prepare solutions of known concentration, calculate reaction stoichiometry, perform titrations, and standardize reagents. Most chemical reactions in solution require knowing the molarity of the reactants.
For educational and planning use. Always prepare solutions to a mark in a volumetric flask, confirm molar mass and purity from the reagent label, and follow your lab safety rules when handling chemicals.