askvity

How to Prepare a Normality Solution?

Published in Solution Preparation 4 mins read

To prepare a solution with a specific Normality, you'll need to follow a systematic approach involving calculations and careful measurements. Here’s a breakdown of the process:

Understanding Normality

Normality (N) is a measure of concentration that expresses the number of gram equivalent weights of solute per liter of solution. It’s often used in acid-base chemistry and redox reactions.

Steps to Prepare a Normality Solution

Here's a step-by-step guide based on the provided reference:

  1. Determine the Equivalent Mass:

    • This is the crucial first step. The equivalent mass of a substance is its molar mass divided by the number of reactive units (e.g., H+ ions for acids, OH- ions for bases, or electrons transferred in a redox reaction).
    • For example:
      • For sulfuric acid (H₂SO₄), which has 2 replaceable hydrogen ions, the equivalent mass is the molar mass divided by 2.
      • For hydrochloric acid (HCl), which has 1 replaceable hydrogen ion, the equivalent mass is the same as its molar mass.

  2. Calculate the Grams Needed:

    • Once you know the equivalent mass, you can calculate the grams of the solute needed for your desired Normality and volume.
    • Formula: Grams needed = (Normality desired) x (Equivalent mass) x (Volume in liters)

  3. Convert Grams to Volume (If starting with a concentrated liquid):

    • If your solute is a concentrated solution rather than a solid, you'll need to use its density to convert grams into milliliters.
    • Formula: Volume = Mass / Density

  4. Dissolve the Solute:

    • Carefully weigh out the calculated amount of solute (either solid or liquid).
    • Dissolve it in a portion of the solvent (usually deionized water).

  5. Bring to Final Volume:

    • Transfer the dissolved solution into a volumetric flask of the desired final volume.
    • Add more solvent until the solution reaches the mark on the flask. Make sure the meniscus is at the line.
    • Mix the solution thoroughly for uniformity.

Example: Preparing 1N HCl Solution

Let's go through an example to illustrate the process.

  1. Equivalent Mass:

    • The molar mass of HCl is approximately 36.46 g/mol. Since HCl has one replaceable hydrogen ion, its equivalent mass is also 36.46 g/eq.

  2. Calculate Grams for 1 Liter:

    • To make 1 liter of 1N HCl solution:
      Grams Needed = 1 N x 36.46 g/eq x 1 L = 36.46 g
      • This assumes 100% purity of the HCl source, which would be extremely dangerous to work with. Therefore, consider the source.

  3. Calculating Volume needed from Concentrate:

    • If a concentrated solution is being used, such as 12.1M HCl, the density of the concentrated solution is needed. Density of 12.1M HCl is about 1.19 g/ml.
    • First, we need the mass of the concentrate.
      • 1 Molar solution of HCL is equal to 1 Normal Solution of HCL, so we want a 1 Liter of 1N solution, this requires 36.46 grams of HCL.
    • So, if the concentrate is 12.1 M solution, then that is equivalent to 12.1 N HCl.
    • Ratio to reach 1 N = 12.1 N / 1 N = 12.1
    • Therefore, using the concentrate, we will need 1/12.1 Liters of it.
    • 1/12.1 = .0826 Liters or 82.6 ml
    • Formula: Volume = (36.46 g / 1.19 g/ml) / 12.1 = 2.53 ml.
  • Thus, 2.53 ml of 12.1 M HCL would need to be diluted into 1 Liter solution.
  1. Procedure:
    • Safety Precautions: Use proper personal protective equipment (PPE) such as safety goggles, gloves, and lab coat while working with acids.
    • Carefully measure 2.53 ml of 12.1 M HCL concentrate in a graduated cylinder or pipette.
    • Add 2.53 ml of the acid to about 500 mL of deionized water in a 1 Liter volumetric flask.
    • Bring the total volume to the 1 Liter mark by adding deionized water carefully.
    • Mix the solution thoroughly.

Practical Considerations:

  • Always use volumetric flasks for precise volume measurements.
  • Use analytical balances for accurate mass measurements.
  • When diluting concentrated acids, always add acid to water slowly while stirring to avoid heat generation (exothermic reaction).
  • Always wear appropriate personal protective equipment (PPE) when handling chemicals.
  • Start with a partially filled volumetric flask. Add the acid to this, then fill up to the volumetric mark with diluent.
  • Double check calculations

By following these steps, you can successfully prepare a Normality solution for your experimental needs.

Related Articles