How Many Moles Are In 68 G Of Copper Hydroxide

How Many Moles Are in 68 g of Copper Hydroxide? A Comprehensive Guide

Determining the number of moles in a given mass of a substance is a fundamental concept in chemistry. This guide will walk you through the process of calculating the number of moles in 68 grams of copper hydroxide, explaining the underlying principles and providing a step-by-step solution. We'll also explore related concepts and applications to solidify your understanding.

Understanding Moles and Molar Mass

Before we delve into the calculation, let's refresh our understanding of key terms:

Mole (mol): The mole is the International System of Units (SI) base unit for the amount of substance. It's a fundamental unit used to count extremely large numbers of atoms, molecules, ions, or other elementary entities. One mole contains Avogadro's number (approximately 6.022 x 10²³) of these entities.

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

Calculating the Molar Mass of Copper Hydroxide

Copper hydroxide, Cu(OH)₂, is an inorganic compound. To calculate its molar mass, we need the atomic masses of its constituent elements: copper (Cu), oxygen (O), and hydrogen (H). You can find these values on a periodic table. The approximate values are:

• Cu: 63.55 g/mol
• O: 16.00 g/mol
• H: 1.01 g/mol

Now, let's calculate the molar mass of Cu(OH)₂:

• Cu: 1 x 63.55 g/mol = 63.55 g/mol
• O: 2 x 16.00 g/mol = 32.00 g/mol
• H: 2 x 1.01 g/mol = 2.02 g/mol

Total molar mass of Cu(OH)₂ = 63.55 + 32.00 + 2.02 = 97.57 g/mol

This means that one mole of copper hydroxide weighs 97.57 grams.

Calculating Moles from Mass

Now we can finally calculate the number of moles in 68 grams of copper hydroxide. We'll use the following formula:

Moles (mol) = Mass (g) / Molar Mass (g/mol)

Plugging in the values:

Moles = 68 g / 97.57 g/mol ≈ 0.697 moles

Therefore, there are approximately 0.697 moles of copper hydroxide in 68 grams of the compound.

Understanding Significant Figures

It's crucial to pay attention to significant figures in chemical calculations. Our initial mass of 68 g has two significant figures. The molar mass we calculated (97.57 g/mol) has four significant figures. When performing calculations, the final answer should have the same number of significant figures as the measurement with the fewest significant figures. Therefore, our final answer of 0.697 moles should be rounded to 0.70 moles to reflect the two significant figures in the given mass.

Applications and Further Exploration

The ability to convert between mass and moles is essential in various chemical calculations and applications. Here are a few examples:

1. Stoichiometry

Stoichiometry involves using balanced chemical equations to determine the quantitative relationships between reactants and products in a chemical reaction. Knowing the number of moles of a reactant allows you to calculate the number of moles of products formed or the amount of other reactants needed.

2. Solution Chemistry

In solution chemistry, molarity (moles per liter) is a crucial concentration unit. Knowing the number of moles of a solute allows you to calculate its molarity in a given volume of solution.

3. Gas Laws

The ideal gas law (PV = nRT) relates the pressure (P), volume (V), temperature (T), and number of moles (n) of a gas. Knowing the number of moles allows you to calculate other properties of the gas.

4. Titrations

Titrations are used to determine the concentration of a solution by reacting it with a solution of known concentration. Calculations involved in titrations often rely on mole-to-mole conversions.

Potential Sources of Error

Several factors can introduce errors into the calculations:

• Impurities in the sample: If the 68g sample of copper hydroxide contains impurities, the actual amount of copper hydroxide will be less than 68g, leading to an inaccurate mole calculation.
• Measurement errors: Inaccurate weighing of the sample can also affect the result. Using a calibrated balance is crucial for minimizing this type of error.
• Rounding errors: Rounding off numbers during intermediate steps can accumulate and affect the final result. It's best to keep extra significant figures until the final calculation to minimize this error.

Conclusion

Calculating the number of moles in a given mass of a substance is a straightforward process once you understand the concept of molar mass. In this guide, we determined that there are approximately 0.70 moles in 68 grams of copper hydroxide. This fundamental calculation is crucial for various applications in chemistry, from stoichiometry and solution chemistry to gas laws and titrations. Understanding significant figures and potential sources of error are vital for ensuring the accuracy and reliability of your calculations. Remember to always double-check your work and use a periodic table for the most accurate atomic masses. By mastering this concept, you will gain a stronger foundation in your understanding of chemistry and its applications.