How many moles are in 68 grams of copper (II) hydroxide, Cu(OH)2?
The correct answer and explanation is :
To determine the number of moles in 68 grams of copper(II) hydroxide (Cu(OH)₂), we need to follow these steps:
Step 1: Determine the Molar Mass of Cu(OH)₂
The molar mass is the sum of the atomic masses of all the atoms in a formula. We can use the periodic table to find the atomic masses of each element:
- Copper (Cu) has an atomic mass of approximately 63.55 g/mol.
- Oxygen (O) has an atomic mass of approximately 16.00 g/mol.
- Hydrogen (H) has an atomic mass of approximately 1.008 g/mol.
Now, let’s calculate the molar mass of Cu(OH)₂:
[
\text{Molar Mass of Cu(OH)₂} = 63.55 \, (\text{Cu}) + 2 \times (16.00 \, (\text{O}) + 1.008 \, (\text{H}))
]
[
\text{Molar Mass of Cu(OH)₂} = 63.55 + 2 \times (16.00 + 1.008)
]
[
\text{Molar Mass of Cu(OH)₂} = 63.55 + 2 \times 17.008 = 63.55 + 34.016 = 97.566 \, \text{g/mol}
]
Step 2: Use the Formula to Find Moles
The number of moles ((n)) is given by the formula:
[
n = \frac{\text{mass}}{\text{molar mass}}
]
We are given the mass as 68 grams, and we just calculated the molar mass of Cu(OH)₂ to be 97.566 g/mol. So, we can substitute the values into the equation:
[
n = \frac{68 \, \text{g}}{97.566 \, \text{g/mol}}
]
[
n = 0.696 \, \text{mol}
]
Conclusion:
Therefore, there are approximately 0.696 moles of copper(II) hydroxide in 68 grams.
Explanation:
The number of moles tells us how many “entities” (atoms, molecules, or formula units) are present in a given mass of a substance. The relationship between mass and moles is crucial in stoichiometry and chemical reactions, as it helps us understand the proportions of substances involved. By using the molar mass, which is a conversion factor between grams and moles, we can calculate how much of a substance is present in terms of moles from a given mass.