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Convert molarity (M) to percent concentration with our free online calculator. Perfect for chemistry labs, solution preparation, and analytical work.
Common: NaCl=58.44, HCl=36.46, NaOH=40.00, H2SO4=98.08
For dilute solutions, use 1.0 g/mL (water density)
Where M = molarity (mol/L), MW = molecular weight (g/mol), density in g/mL
Example conversions for NaCl (MW = 58.44 g/mol, density ≈ 1.0 g/mL):
| Molarity (M) | Percent (% w/v) |
|---|---|
| 0.1 M | 0.5844% |
| 0.5 M | 2.922% |
| 1.0 M | 5.844% |
| 1.5 M | 8.766% |
| 2.0 M | 11.688% |
| 3.0 M | 17.532% |
| 4.0 M | 23.376% |
| 5.0 M | 29.220% |
| 6.0 M | 35.064% |
| 10.0 M | 58.440% |
Molarity (M) is a unit of concentration that expresses the number of moles of solute per liter of solution. It's one of the most commonly used concentration units in chemistry because it directly relates to the number of molecules or ions in solution. A 1 M solution contains 1 mole of solute dissolved in enough solvent to make 1 liter of total solution. This makes molarity ideal for stoichiometric calculations and understanding chemical reactions in solution.
Percent concentration (% w/v or weight/volume) expresses the mass of solute in grams per 100 mL of solution. Converting between these units requires knowledge of the molecular weight and solution density, as molarity is based on moles while percent is based on mass.
Look up or calculate the molecular weight (MW) of your solute in grams per mole. For example, NaCl has MW = 58.44 g/mol.
For dilute aqueous solutions, you can use 1.0 g/mL (density of water). For concentrated solutions, refer to density tables.
Use the formula: % (w/v) = (M × MW) / (10 × density). Multiply your molarity by molecular weight, then divide by 10 times the density.
Perform the calculation and verify your result makes sense. For example, 1 M NaCl ≈ 5.844% w/v.
Remember that this conversion assumes ideal solution behavior. Very concentrated solutions may require more precise density values.
Molarity (M) measures concentration in moles per liter, based on the number of particles, while percent (% w/v) measures mass in grams per 100 mL, based on weight. Molarity is preferred for reactions because it relates directly to stoichiometry, while percent is often used in clinical and industrial settings.
Molecular weight connects the number of moles (used in molarity) to the mass of solute (used in percent). Without it, you cannot convert between these fundamentally different ways of expressing concentration. Different compounds with the same molarity have different percent concentrations.
For dilute aqueous solutions (less than 5-10% concentration), you can usually approximate the density as 1.0 g/mL, the density of pure water. For more concentrated solutions, especially of dense compounds, you should use the actual solution density from tables or measurements.
% w/v (weight/volume) is grams per 100 mL, % w/w (weight/weight) is grams per 100 grams, and % v/v (volume/volume) is mL per 100 mL. The conversion from molarity typically yields % w/v. Each is used in different contexts depending on how the solution is prepared.
Temperature affects solution density and, to a lesser extent, molarity (since volume changes with temperature). For precise work at different temperatures, use temperature-corrected density values. For most laboratory work at room temperature, standard values are acceptable.
Yes, this conversion works for any solute if you know its molecular weight and the solution density. It's commonly used for salts, acids, bases, and organic compounds. For electrolytes that dissociate, remember that molarity refers to the formula unit, not individual ions.