how many molecules are in 3.9 grams of sodium chloride

Lussy04

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24-01-2025

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Meta Description: Discover how to calculate the number of molecules in a given mass of sodium chloride (NaCl). This guide breaks down the steps, explains the concepts, and provides a clear solution to the problem: how many molecules are in 3.9 grams of NaCl? Learn about molar mass, Avogadro's number, and more!

Understanding the Calculation

To determine the number of molecules in 3.9 grams of sodium chloride (NaCl), we need to use a few key concepts from chemistry:

• Molar Mass: This is the mass of one mole of a substance. A mole is a unit representing a specific number of particles (atoms, molecules, ions, etc.), defined by Avogadro's number.

• Avogadro's Number: This fundamental constant in chemistry is approximately 6.022 x 10²³. It represents the number of particles in one mole of any substance.

• Conversion Factors: We'll use molar mass and Avogadro's number as conversion factors to move from grams to molecules.

Step-by-Step Calculation

Here's how to calculate the number of molecules in 3.9 grams of NaCl:

1. Find the Molar Mass of NaCl:

• The atomic mass of sodium (Na) is approximately 22.99 g/mol.
• The atomic mass of chlorine (Cl) is approximately 35.45 g/mol.
• Therefore, the molar mass of NaCl is 22.99 g/mol + 35.45 g/mol = 58.44 g/mol.

2. Convert Grams to Moles:

We have 3.9 grams of NaCl. To convert this to moles, we use the molar mass as a conversion factor:

(3.9 g NaCl) x (1 mol NaCl / 58.44 g NaCl) ≈ 0.0667 mol NaCl

3. Convert Moles to Molecules:

Now, we use Avogadro's number (6.022 x 10²³ molecules/mol) to convert moles to the number of molecules:

(0.0667 mol NaCl) x (6.022 x 10²³ molecules NaCl / 1 mol NaCl) ≈ 4.01 x 10²² molecules NaCl

The Answer

Therefore, there are approximately 4.01 x 10²² molecules in 3.9 grams of sodium chloride.

Important Considerations

• Significant Figures: The number of significant figures in our answer (two) is limited by the precision of the given mass (3.9 grams).

• Ionic Compound: NaCl is an ionic compound, meaning it exists as a lattice of ions (Na⁺ and Cl^-) rather than discrete molecules. However, the term "molecule" is often used loosely in this context to refer to a formula unit of NaCl.

• Approximations: Atomic masses are approximate values. Using more precise atomic masses would slightly alter the final result.

Further Exploration: Calculating Molecules in Other Compounds

The same method can be applied to calculate the number of molecules in a given mass of any other compound. Simply replace the molar mass of NaCl with the molar mass of the desired compound. This requires calculating the molar mass based on the atomic masses of the constituent elements in the chemical formula. Remember to always use proper units and conversion factors for accurate results.