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Solution Concentration Calculator

Concentration is a measure of the amount of solute in a given amount of solvent or solution. Several common concentration units are used: Molarity (M = mol/L), Molality (m = mol/kg solvent), and Mass Percent (% mass of solute / mass of solution). Molarity is the most frequently used concentration unit, expressing moles of solute per liter of solution. Molality is not affected by temperature because it uses the mass of solvent. Mass percent is useful for solid solutions or high concentrations.

M = n/V; m = n/mass of solvent; % mass = (mass of solute/mass of solution) × 100%

Variables:

  • MMolarity
    (e.g.: 1 M)
  • mMolality
    (e.g.: 1 m)
  • nNumber of moles
    (e.g.: 0.5 mol)
  • VSolution volume
    (e.g.: 0.5 L)
  • %Mass percent
    (e.g.: 10%)

Categories:

How to Use the Calculator

  1. 1

    Select Unit

    Choose concentration unit: Molarity, Molality, or Mass Percent.

  2. 2

    Enter Data

    Enter moles, volume, or mass as required by the selected unit.

  3. 3

    Calculate

    Click calculate to convert between units.

Examples

Calculating Molarity

Problem:

Dissolve 2 mol NaCl in water to a volume of 500 mL. What is the molarity?

Solution:
  1. 1.M = n/V
  2. 2.M = 2 / 0.5
  3. 3.M = 4 M
Result:4 M

The NaCl solution concentration is 4 molar.

Calculating Molality

Problem:

1 mol sugar dissolved in 500 grams of water. What is the molality?

Solution:
  1. 1.m = n / mass of solvent (kg)
  2. 2.m = 1 / 0.5
  3. 3.m = 2 m
Result:2 m

The sugar solution molality is 2 molal.

Frequently Asked Questions

What is the difference between molarity and molality?
Molarity (M) uses solution volume (which changes with temperature), while molality (m) uses solvent mass (unaffected by temperature). Molality is more accurate for colligative property calculations.
When should I use mass percent?
Mass percent is used for high-concentration solutions, solid-in-solid mixtures, or when mass is easier to measure than volume (e.g., salt in food, metal alloys).

Related Calculators

Mole Calculator

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Colligative Properties

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pH Calculator

Uses molarity

References