A calcium sample weighting 607.4 mg was precipitated as oxalate and calcined calcium carbonate giving 246.7 mg. What the percentage of calcium in the sample?
Calcium molecular weight: 40.078 g/mol
CaCO3 molecular weight: 100 g/mol
To calculate the percentage of calcium in the sample, we first need to determine the amount of calcium present in the calcined calcium carbonate.
The sample, weighing 607.4 mg, was precipitated as oxalate and then calcined to form calcium carbonate, which weighed 246.7 mg. This means that the difference in weight between the original sample and the calcined calcium carbonate is due to the loss of other components, leaving behind only calcium.
To find the amount of calcium in the 246.7 mg of calcium carbonate, we need to calculate the amount in moles.
First, let's calculate the number of moles of CaCO3:
Molar mass of CaCO3 = 100 g/mol
Mass of CaCO3 = 246.7 mg = 0.2467 g
Number of moles of CaCO3 = mass / molar mass
= 0.2467 g / 100 g/mol
= 0.002467 mol
Since the molar ratio of calcium (Ca) to calcium carbonate (CaCO3) is 1:1, the number of moles of calcium will also be 0.002467 mol.
Now, let's calculate the amount of calcium in grams:
Molar mass of calcium (Ca) = 40.078 g/mol
Mass of calcium = number of moles x molar mass
= 0.002467 mol x 40.078 g/mol
= 0.09897 g
Finally, we can calculate the percentage of calcium in the original sample:
Percentage of calcium = (mass of calcium / mass of sample) x 100
= (0.09897 g / 607.4 mg) x 100
= 16.28%
Therefore, the percentage of calcium in the sample is approximately 16.28%.