Cal11 calculator
Search calculator...

5 9 Calculate The Molarity and Normality of The Following

Reviewed by Calculator Editorial Team

This guide explains how to calculate molarity and normality of chemical solutions, including the formulas, differences between the two concepts, and practical examples.

What are Molarity and Normality?

Molarity and normality are both measures of concentration in chemistry, but they are calculated differently and have different applications.

Molarity (M) is defined as the number of moles of solute dissolved in one liter of solution. It is calculated using the formula:

M = moles of solute / liters of solution

Normality (N) is defined as the number of equivalents of solute dissolved in one liter of solution. It is calculated using the formula:

N = equivalents of solute / liters of solution

Molarity is commonly used in stoichiometric calculations, while normality is often used in acid-base titrations and redox reactions.

How to Calculate Molarity

To calculate molarity, you need to know the number of moles of solute and the volume of the solution in liters. Here's a step-by-step guide:

  1. Determine the mass of the solute.
  2. Convert the mass to moles using the molar mass of the solute.
  3. Determine the volume of the solution in liters.
  4. Divide the number of moles by the volume in liters to get the molarity.

Molarity Formula:

M = moles of solute / liters of solution

For example, if you have 5 moles of sodium chloride (NaCl) dissolved in 2 liters of water, the molarity would be:

M = 5 moles / 2 L = 2.5 M

How to Calculate Normality

To calculate normality, you need to know the number of equivalents of solute and the volume of the solution in liters. Here's a step-by-step guide:

  1. Determine the mass of the solute.
  2. Convert the mass to equivalents using the equivalent weight of the solute.
  3. Determine the volume of the solution in liters.
  4. Divide the number of equivalents by the volume in liters to get the normality.

Normality Formula:

N = equivalents of solute / liters of solution

For example, if you have 9 equivalents of sulfuric acid (H₂SO₄) dissolved in 3 liters of water, the normality would be:

N = 9 equivalents / 3 L = 3 N

Difference Between Molarity and Normality

While both molarity and normality measure concentration, they are calculated differently and have different applications:

  • Molarity is based on the number of moles of solute, making it useful for stoichiometric calculations.
  • Normality is based on the number of equivalents of solute, making it useful for acid-base titrations and redox reactions.
  • Molarity is commonly used in general chemistry, while normality is often used in analytical chemistry.

Remember that 1 equivalent is equal to the charge on one ion in a reaction. For example, sulfuric acid (H₂SO₄) has two equivalents because it can donate two protons (H⁺ ions).

Example Calculation

Let's calculate the molarity and normality of a solution containing 5 grams of sodium hydroxide (NaOH) dissolved in 1 liter of water.

Step 1: Calculate Molarity

  1. Molar mass of NaOH = 40 g/mol
  2. Moles of NaOH = mass / molar mass = 5 g / 40 g/mol = 0.125 moles
  3. Volume of solution = 1 L
  4. Molarity = moles / volume = 0.125 moles / 1 L = 0.125 M

Step 2: Calculate Normality

  1. NaOH is a strong base with a valence of 1, so each mole of NaOH provides 1 equivalent.
  2. Equivalents of NaOH = moles = 0.125 equivalents
  3. Volume of solution = 1 L
  4. Normality = equivalents / volume = 0.125 equivalents / 1 L = 0.125 N

In this case, the molarity and normality of the solution are the same because NaOH has a valence of 1.

FAQ

What is the difference between molarity and normality?

Molarity is based on the number of moles of solute, while normality is based on the number of equivalents of solute. Molarity is useful for stoichiometric calculations, while normality is often used in acid-base titrations and redox reactions.

How do you calculate molarity?

Molarity is calculated by dividing the number of moles of solute by the volume of the solution in liters. The formula is M = moles of solute / liters of solution.

How do you calculate normality?

Normality is calculated by dividing the number of equivalents of solute by the volume of the solution in liters. The formula is N = equivalents of solute / liters of solution.

When should you use molarity instead of normality?

Use molarity for stoichiometric calculations and when dealing with reactions where the number of moles is directly relevant. Use normality for acid-base titrations and redox reactions where the number of equivalents is more important.