what is the percent composition for each element in magnesium chloride?
The Correct Answer and Explanation is:
The percent composition of an element in a compound tells us what fraction of the total mass of the compound comes from that element. To calculate the percent composition of each element in magnesium chloride (MgCl₂), we need to first determine the molar mass of the compound and then calculate the mass contribution of each element.
Step 1: Find the molar mass of MgCl₂
- Magnesium (Mg) has a molar mass of 24.31 g/mol.
- Chlorine (Cl) has a molar mass of 35.45 g/mol.
Since there are two chlorine atoms in magnesium chloride, the molar mass of MgCl₂ is calculated as: Molar mass of MgCl₂=24.31 g/mol+2×35.45 g/mol\text{Molar mass of MgCl₂} = 24.31 \, \text{g/mol} + 2 \times 35.45 \, \text{g/mol}Molar mass of MgCl₂=24.31g/mol+2×35.45g/mol Molar mass of MgCl₂=24.31 g/mol+70.90 g/mol=95.21 g/mol\text{Molar mass of MgCl₂} = 24.31 \, \text{g/mol} + 70.90 \, \text{g/mol} = 95.21 \, \text{g/mol}Molar mass of MgCl₂=24.31g/mol+70.90g/mol=95.21g/mol
Step 2: Calculate the mass contribution of each element
- The mass of magnesium (Mg) in MgCl₂ is 24.31 g.
- The mass of chlorine (Cl) in MgCl₂ is 2 × 35.45 g = 70.90 g.
Step 3: Calculate the percent composition of each element
The percent composition is calculated by dividing the mass of each element by the total molar mass of the compound and then multiplying by 100.
- Percent composition of magnesium (Mg):
24.31 g95.21 g/mol×100=25.55%\frac{24.31 \, \text{g}}{95.21 \, \text{g/mol}} \times 100 = 25.55\%95.21g/mol24.31g×100=25.55%
- Percent composition of chlorine (Cl):
70.90 g95.21 g/mol×100=74.45%\frac{70.90 \, \text{g}}{95.21 \, \text{g/mol}} \times 100 = 74.45\%95.21g/mol70.90g×100=74.45%
Final Answer:
- The percent composition of magnesium (Mg) in magnesium chloride is 25.55%.
- The percent composition of chlorine (Cl) in magnesium chloride is 74.45%.
This method shows how the total mass of each element contributes to the compound’s overall mass.
