Calculating the Number of Moles of NaCl in 15 g of NaCl: A Comprehensive Guide

Introduction

Understanding the molecular composition of substances, specifically the number of moles, is fundamental in chemistry. The calculation of moles involves the use of the substance's molar mass. This article will guide you through the process of determining the number of moles of sodium chloride (NaCl) in a given amount of substance, emphasizing the steps involved and providing a clear explanation.

Understanding Molar Mass

Before diving into the calculation, it's necessary to understand the concept of molar mass. The molar mass of a compound is the sum of the atomic weights of all the atoms that make up the molecule. For NaCl, we need to add the atomic masses of sodium (Na) and chlorine (Cl).

Atomic Masses

Sodium (Na): Approximately 23 g/mol Chlorine (Cl): Approximately 35.5 g/mol

Total Molar Mass of NaCl

Molar mass of NaCl 23 g/mol 35.5 g/mol 58.5 g/mol

Step-by-Step Calculation

To find the number of moles of NaCl in 15 g of NaCl, we use the formula:

Number of moles frac{mass (g)}{molar mass (g/mol)}

Detailed Calculation

Given that the mass of NaCl is 15 g and the molar mass is 58.5 g/mol, the calculation proceeds as follows:

Number of moles frac{15 g}{58.5 g/mol} approx 0.2564 moles

Therefore, there are approximately 0.256 moles of NaCl in 15 g of NaCl.

Using Units or Dimensional Analysis

Maintaining units during the calculation is crucial for accuracy. Using dimensional analysis, we can express the calculation as:

If 58.5 g of sodium chloride is the mass of 1.0 mole, then 15 g of sodium chloride is the mass of x moles. Translating this to an equation, we have:

x (1.0 mol NaCl / 58.5 g) * 15.0 g 0.26 mol

This approach confirms the previous calculation and highlights the importance of maintaining unit consistency.

Verification of Calculation

Again, let's verify the calculation using the molar mass of NaCl, which is 58.46 g/mol (rounded from 58.5 g/mol):

n_{Na^{}Cl^{-}}frac{15.0g}{58.46gmol^{-1}}

Performing the division results in:

n_{Na^{}Cl^{-}} approx 0.257 moles

This value slightly differs due to rounding but is sufficiently accurate for most practical purposes.

Conclusion

Through this comprehensive guide, we have discussed the calculation of moles in a practical example involving NaCl. The process involves the determination of the molar mass and the application of the formula: Number of moles mass (g) / molar mass (g/mol). Understanding this principle is essential for various chemical reactions and equations. Whether you are a student or a professional in chemistry, mastering these calculations will significantly enhance your analytical skills.