Calculate molar concentration of solutions in mol/L (M)
Chemical Calculator
Molarity — Quick answer
Molarity (M) is the amount of solute (in moles) per litre of solution. It is the most common concentration unit in chemistry and the basis for the dilution equation C1V1 = C2V2.
M = n / V | n = m / MW | C1V1 = C2V2
M — molarity (mol/L)
n — moles of solute
V — volume of solution in litres
m — mass of solute (g)
MW — molar mass (g/mol)
C, V (1/2) — concentration and volume before / after dilution
Worked example: Prepare 250 mL of 0.10 M NaCl. MW(NaCl) = 58.44 g/mol. Mass = M × V × MW = 0.10 × 0.250 × 58.44 = 1.46 g. Dilute to 250 mL with deionised water. To make 100 mL of 0.020 M from this stock: V1 = (0.020 × 100) / 0.10 = 20 mL stock + 80 mL water.
Common laboratory stock concentrations
Reagent
Stock (M)
Typical working (M)
HCl (37% w/w)
12.1
0.1 – 1.0
H2SO4 (98% w/w)
18.0
0.1 – 1.0
NaOH pellets
10.0 (from solid)
0.1 – 1.0
NH4OH (28% w/w)
14.8
0.1 – 1.0
Acetic acid (glacial)
17.4
0.1 – 1.0
Standard / source: IUPAC Green Book Section 2.10 (Chemical thermodynamics).
This calculator uses the standard molarity calculator formula:
Molarity Formula
M = n / V (mol/L)
Frequently Asked Questions
What is molarity?⌄
Molarity (M) is the number of moles of solute dissolved per litre of solution: M = n ÷ V. It is the most common way to express solution concentration.
What is the molarity of 5.85 g of NaCl in 500 mL?⌄
NaCl molar mass = 58.44 g/mol. Moles = 5.85 ÷ 58.44 = 0.1001 mol. Molarity = 0.1001 ÷ 0.5 L = 0.200 mol/L (0.2 M).
What is the difference between molarity and molality?⌄
Molarity (M) = moles per litre of solution. Molality (m) = moles per kilogram of solvent. Molality is temperature-independent; molarity is not.
How do I prepare a 1 M solution?⌄
Weigh out 1 mole of solute (mass = molar mass in grams), dissolve it in solvent, and transfer to a 1-litre volumetric flask. Fill to the 1-litre mark with solvent.
What is normality vs molarity?⌄
Normality (N) = Molarity × number of equivalents (n-factor). For HCl, n=1 so 1 M = 1 N. For H₂SO₄, n=2 so 1 M = 2 N.
How does temperature affect molarity?⌄
Temperature changes the volume of the solution, which changes molarity. A solution heated up becomes less concentrated as the volume expands.
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