How Many Moles Are Contained In 23.5 G Of Sb2s3

How Many Moles Are Contained in 23.5 g of Sb₂S₃? A Comprehensive Guide to Mole Calculations

This article provides a comprehensive guide to calculating the number of moles in a given mass of a compound, specifically focusing on 23.5 g of antimony(III) sulfide (Sb₂S₃). We will explore the fundamental concepts of molar mass, Avogadro's number, and stoichiometry, illustrating the step-by-step process with detailed explanations and examples. This approach will equip you with the knowledge to tackle similar problems involving mole calculations and strengthen your understanding of chemical stoichiometry.

Understanding Moles and Molar Mass

Before diving into the calculations, let's refresh our understanding of fundamental concepts:

• The Mole (mol): The mole is the International System of Units (SI) base unit for the amount of substance. It represents a specific number of entities (atoms, molecules, ions, etc.), defined as Avogadro's number (approximately 6.022 x 10²³). One mole of any substance contains Avogadro's number of particles.

• Molar Mass (g/mol): The molar mass of a substance is the mass of one mole of that substance. It's numerically equal to the atomic weight (for elements) or the molecular weight (for compounds) expressed in grams per mole (g/mol).

Calculating the Molar Mass of Sb₂S₃

To determine the number of moles in 23.5 g of Sb₂S₃, we first need to calculate its molar mass. This involves summing the atomic masses of all the atoms in the molecule:

• Atomic Mass of Antimony (Sb): Approximately 121.76 g/mol
• Atomic Mass of Sulfur (S): Approximately 32.07 g/mol

The molecular formula of antimony(III) sulfide is Sb₂S₃, indicating two antimony atoms and three sulfur atoms per molecule. Therefore, the molar mass of Sb₂S₃ is:

(2 x Atomic mass of Sb) + (3 x Atomic mass of S) = (2 x 121.76 g/mol) + (3 x 32.07 g/mol) = 243.52 g/mol + 96.21 g/mol = 339.73 g/mol

Calculating the Number of Moles in 23.5 g of Sb₂S₃

Now that we know the molar mass of Sb₂S₃, we can calculate the number of moles present in 23.5 g using the following formula:

Number of moles = Mass (g) / Molar mass (g/mol)

Plugging in the values:

Number of moles = 23.5 g / 339.73 g/mol = 0.06917 moles

Therefore, there are approximately 0.06917 moles of Sb₂S₃ in 23.5 g of the compound.

Understanding Significant Figures

It's crucial to consider significant figures in scientific calculations. The given mass (23.5 g) has three significant figures. Our calculated molar mass (339.73 g/mol) has five significant figures, but we should round it to three significant figures to match the precision of the given mass. Thus, a more accurate representation of the molar mass would be 340 g/mol.

Using the rounded molar mass:

Number of moles = 23.5 g / 340 g/mol = 0.0691 moles

This adjusted result, 0.0691 moles, reflects the appropriate number of significant figures.

Relating Moles to Avogadro's Number

Remember, one mole contains Avogadro's number (6.022 x 10²³) of particles. To determine the number of Sb₂S₃ molecules in 23.5 g:

Number of molecules = Number of moles x Avogadro's number = 0.0691 moles x 6.022 x 10²³ molecules/mol = 4.16 x 10²² molecules

This calculation shows that approximately 4.16 x 10²² molecules of Sb₂S₃ are present in 23.5 g of the compound.

Practical Applications and Further Exploration

The ability to convert between mass and moles is fundamental in various chemical applications, including:

• Stoichiometric Calculations: Determining the amounts of reactants and products in chemical reactions.
• Solution Chemistry: Calculating concentrations of solutions (molarity, molality).
• Analytical Chemistry: Performing quantitative analyses of substances.

Expanding on the Concept:

This example focuses on a single compound. However, the principles of mole calculations can be extended to more complex scenarios involving chemical reactions and mixtures. For instance:

• Reactions involving multiple reactants and products: You can use mole calculations to determine limiting reactants and theoretical yields.
• Mixtures of compounds: You can calculate the moles of each component in a mixture if you know the mass of each component and its molar mass.

Troubleshooting and Common Mistakes

Several common mistakes can arise when performing mole calculations:

• Incorrect Molar Mass Calculation: Ensure you correctly calculate the molar mass by summing the atomic masses of all atoms in the molecule, accounting for the correct number of each atom.
• Unit Errors: Always pay close attention to units. Ensure consistency between mass (g), molar mass (g/mol), and the final units (moles).
• Significant Figures: Follow significant figure rules to report the final answer with the correct precision.

Conclusion

Calculating the number of moles in a given mass of a substance is a crucial skill in chemistry. By understanding molar mass, Avogadro's number, and applying the appropriate formulas, you can accurately determine the number of moles and further extend this knowledge to solve more complex stoichiometric problems. This guide provides a comprehensive framework for mastering these calculations and applying them to various chemical scenarios, enabling you to confidently work with chemical quantities. Remember to always double-check your calculations, pay attention to significant figures, and understand the underlying principles. This will ensure accuracy and improve your problem-solving abilities in chemistry.