Understanding the Normality of a 10% NaOH Solution

When dealing with solutions, it is essential to understand the properties and characteristics of such solutions, particularly when working with sodium hydroxide (NaOH). This article delves into the calculation of the normality of a 10% NaOH solution, providing a comprehensive guide that helps in understanding the concept of normality and its relation to molarity. We will also cover the molar mass of NaOH, how to calculate the number of moles, and the difference between normality and molarity.

Molar Mass of NaOH

The molar mass of a substance is the mass of one mole of that substance. For NaOH, it is calculated as follows:

Molecular Weight of NaOH: Sodium (Na) 23 g/mol, Oxygen (O) 16 g/mol, Hydrogen (H) 1 g/mol. Total Molecular Weight of NaOH 23 16 1 40 g/mol.

This value is crucial for understanding the solution's behavior and concentration.

10% (w/v) NaOH Solution

A 10% (w/v) solution of NaOH means that there are 10 grams of NaOH in 100 mL of the solution. This information is key to understanding the solution's composition and concentration.

Molarity (M) moles of solute / liters of solution. Calculating moles of NaOH in 10 g: 10 g / 40 g/mol 0.25 mol. Since 10 g is in 100 mL or 0.1 L, the molarity is: 2.5 M.

The molarity of a 10% NaOH solution is 2.5 M.

Calculating Normality

Normality (N) is a measure of concentration used in chemistry, especially in the context of titrations and acid-base reactions. For NaOH, which is a strong base and dissociates completely into Na? and OH? ions, the normality can be calculated as follows:

Number of equivalents per mole of NaOH 1 (since NaOH produces one OH? ion per mole). Normality Molarity × number of equivalents 2.5 M × 1 2.5 N.

Hence, the normality of a 10% NaOH solution is 2.5 N.

Diluting NaOH Solution

The normality of a 10% NaOH solution is 2.5 N. To dilute this solution and achieve a lower normality, one can follow the steps outlined below:

The normality of the solution can be diluted by 25 times to achieve a normality of 0.1 N. For instance, if you have 1 L of a 2.5 N NaOH solution, diluting it with 24 L of water will result in a 0.1 N solution.

This process is based on the principle that normality is directly proportional to the amount of solute, and thus, dilution reduces the normality proportionally.

Calculations for Normality and Molarity

For a more complex scenario, where the solution has a higher concentration or density, the calculations can be more involved. Here is a detailed example:

Mean Density (D) of the solution 1.1089 g/mL. Mass of NaOH in 1 L of solution (m) 0.1 L × 1.1089 g/mL × 1000 mL 110.89 g. Moles of NaOH in 1 L of solution 110.89 g / 40 g/mol 2.77 mol. Normality of the solution 2.77 mol/L 2.77 N.

This example illustrates how to calculate the normality of a solution with a given density and composition.

Conclusion

Understanding the normality of a 10% NaOH solution is crucial for conducting accurate chemical reactions and titrations. The normality and molarity of NaOH are directly related, and the molar mass of NaOH is a fundamental value that helps in determining the concentration of the solution. By following the steps detailed above, one can easily calculate the normality of NaOH solutions and perform accurate experiments.