Calculate the mass percentage of Al in AlCl3.
The correct answer and explanation is:
Correct Answer:
The mass percentage of aluminum (Al) in aluminum chloride (AlCl₃) is 20.26%.
Explanation:
To calculate the mass percentage of an element in a compound, use the formula: Mass percentage of element=(Mass of element in 1 mole of compoundMolar mass of compound)×100\text{Mass percentage of element} = \left( \frac{\text{Mass of element in 1 mole of compound}}{\text{Molar mass of compound}} \right) \times 100
First, determine the molar mass of aluminum chloride (AlCl₃). This compound contains:
- 1 atom of aluminum (Al)
- 3 atoms of chlorine (Cl)
Using atomic masses from the periodic table:
- Atomic mass of Al = 26.98 g/mol
- Atomic mass of Cl = 35.45 g/mol
Now calculate the total molar mass of AlCl₃: Molar mass of AlCl3=26.98+(3×35.45)=26.98+106.35=133.33 g/mol\text{Molar mass of AlCl}_3 = 26.98 + (3 \times 35.45) = 26.98 + 106.35 = 133.33\ \text{g/mol}
Next, calculate the mass percentage of aluminum: \text{Mass % of Al} = \left( \frac{26.98}{133.33} \right) \times 100 = 20.26\%
This percentage means that in every 100 grams of aluminum chloride, approximately 20.26 grams come from aluminum.
Understanding mass percentage is important in both chemistry and industry. In chemical reactions, it helps determine how much of a certain element is present in a compound, which affects stoichiometric calculations. In industrial applications, knowing the percentage composition helps in cost estimation and material usage. For example, if aluminum is the element of interest, knowing it makes up 20.26% of the compound tells how much pure aluminum can be extracted or used in manufacturing processes involving AlCl₃.