Use the molar mass of Al2(SO4)3 to calculate the number of formula units in 10.0 g of AS. Everything about a chemical formula is a direct proportion. We calculated the molar mass of aluminium sulphate as 342.15 g/mol. In the previous problem we calculated that there are 0.0292274 moles in 10.0 g.
The Correct Answer and Explanation is :
To find the number of formula units in 10.0 g of aluminum sulfate (Al₂(SO₄)₃), we’ll use the moles we have calculated and Avogadro’s number, which gives the number of particles (in this case, formula units) in one mole of a substance.
Step 1: Moles of Aluminum Sulfate
From the given information, we know that the number of moles of aluminum sulfate (Al₂(SO₄)₃) in 10.0 g is 0.0292274 moles. This was calculated using the molar mass of aluminum sulfate (342.15 g/mol) in the previous problem.
Step 2: Avogadro’s Number
Avogadro’s number, 6.022 × 10²³ formula units/mole, is the constant used to convert moles to individual formula units.
Step 3: Formula Units Calculation
To calculate the number of formula units, we multiply the number of moles of the substance by Avogadro’s number:
[
\text{Number of formula units} = \text{moles} \times \text{Avogadro’s number}
]
Substituting the values:
[
\text{Number of formula units} = 0.0292274 \, \text{moles} \times 6.022 \times 10^{23} \, \text{formula units/mole}
]
[
\text{Number of formula units} = 1.759 \times 10^{22} \, \text{formula units}
]
Thus, there are 1.759 × 10²² formula units of aluminum sulfate in 10.0 g.
Explanation
The concept of moles is fundamental to understanding chemical reactions and stoichiometry. A mole is simply a way to count particles, whether atoms, molecules, or formula units, much like a dozen counts 12 objects. The number of particles in one mole is fixed by Avogadro’s number, which is approximately ( 6.022 \times 10^{23} ) particles. This number is constant for any substance, so by knowing the moles of a substance, we can calculate how many individual formula units are present.
In this problem, we were given the number of moles of aluminum sulfate (0.0292274 moles) and its molar mass (342.15 g/mol). Using this information, we converted the amount of aluminum sulfate from grams to moles and then used Avogadro’s number to find the number of formula units in the given sample. This approach allows us to understand the scale of particles in even a small quantity of a substance, helping chemists predict how substances will react in a chemical reaction.