An antacid tablet weighing 3.084 g was dissolved and diluted to 100.0 mL in a volumetric flask. A 25.00-mL aliquot was removed and treated with sufficient 8-hydroxyquinoline to precipitate all of the aluminum and magnesium. After proper collection and drying, this precipitate weighed 1.7748 g. Another 25.00-mL aliquot of the sample was treated with enough ammonia to precipitate just Al(OH)3. After ignition at 800°C, this precipitate weighed 0.1167 g. Calculate the % Al and % Mg in the antacid.
Bhj
To solve this problem, we need to determine the amount of aluminum (Al) and magnesium (Mg) present in the antacid and calculate the percentage of each element.
Let's break down the steps:
1. Calculate the moles of Al and Mg in the precipitate:
- The precipitate obtained from the 25.00 mL aliquot after treatment with 8-hydroxyquinoline contains both Al and Mg.
- Convert the mass of the precipitate (1.7748 g) to moles using the molar mass of the precipitate.
2. Calculate the moles of Al in the second 25.00 mL aliquot:
- The precipitate obtained after treatment with ammonia and ignition consists of only Al.
- Convert the mass of the precipitate (0.1167 g) to moles using the molar mass of Al.
3. Calculate the moles of Mg in the antacid:
- The difference between the total moles of Al and the moles of Al obtained from the second aliquot will give us the moles of Mg.
4. Calculate the percentage of Al and Mg in the antacid:
- Divide the moles of Al and Mg by the total mass of the antacid (3.084 g) and multiply by 100 to get the percentage.
Let's perform these calculations step by step:
1. Calculate the moles of Al and Mg in the precipitate:
- The molar mass of the precipitate can be calculated by adding the molar masses of Al and Mg:
- Molar mass of Al = 26.98 g/mol
- Molar mass of Mg = 24.31 g/mol
- Molar mass of the precipitate = (26.98 g/mol) + (24.31 g/mol) = 51.29 g/mol
- Moles of precipitate = 1.7748 g / 51.29 g/mol
2. Calculate the moles of Al in the second aliquot:
- Molar mass of Al = 26.98 g/mol
- Moles of Al in the second aliquot = 0.1167 g / 26.98 g/mol
3. Calculate the moles of Mg in the antacid:
- Moles of Mg = Moles of precipitate - Moles of Al in the second aliquot
4. Calculate the percentage of Al and Mg in the antacid:
- % Al = (Moles of Al / Total moles) * 100
- % Mg = (Moles of Mg / Total moles) * 100
Finally, substitute the calculated values into these equations to find the percentages of Al and Mg in the antacid.