Molarity Calculator

What is Molarity?

Molarity (M) is a measure of concentration defined as the number of moles of solute per liter of solution:

Molarity (M) = moles of solute / liters of solution

Key Formulas

• M = n / V where n = moles, V = volume in liters
• n = mass / MW where MW = molecular weight (g/mol)
• M = (mass / MW) / V combined formula
• M₁V₁ = M₂V₂ dilution formula

Solution Preparation Steps

1. Calculate the mass of solute needed
2. Weigh the calculated mass accurately
3. Dissolve the solute in less than the final volume of solvent
4. Transfer to a volumetric flask
5. Add solvent to reach the final volume mark
6. Mix thoroughly

Dilution Example

Problem: Prepare 100 mL of 1 M solution from 10 M stock

Solution: Using M₁V₁ = M₂V₂

(10 M)(V₁) = (1 M)(100 mL)

V₁ = 10 mL

Answer: Take 10 mL of stock and dilute to 100 mL total volume

Common Molarity Values

• 1 M NaCl: 58.44 g/L (table salt solution)
• 1 M Glucose: 180.16 g/L (C₆H₁₂O₆)
• 1 M HCl: 36.46 g/L (hydrochloric acid)
• 1 M NaOH: 40.00 g/L (sodium hydroxide)

Tips for Accurate Solutions

• Use analytical-grade chemicals when possible
• Use calibrated volumetric flasks for precision
• Account for temperature (standard is 25°C)
• Store solutions properly (labeled, dated, sealed)
• Consider hydration states of salts (e.g., CuSO₄·5H₂O)

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