An impure sample of Na2SO4 weighed 1.562g. A BaSO4 precipitate from this sample weighed 2.496g. Calculate the percentage of sulfur and the percentage purity of salt.
I assume you want % S IN THE SAMPLE.
a m = atomic mass; m m = molar mass
grams S = 2.496 g BaSO4 x (a m S/m m BaSO4) = 2.496 x (32.06/233.34) = ?
Then %S in the unknown = 100(g S/1.562) = ?
% purity = 100*(mass Na2SO4/mass sample) where mass Na2SO4 is
mass BaSO4 ppt x (m m Na2SO4/m m BaSO4)
Post your work if you get stuck.
To calculate the percentage of sulfur in the impure sample, we need to find the mass of sulfur in the BaSO4 precipitate.
Molar mass of BaSO4 = 137.33 g/mol + 32.06 g/mol + (4 * 16.00 g/mol) = 233.39 g/mol
Mass of sulfur in BaSO4 precipitate = (2 * 32.06 g/mol) = 64.12 g/mol
Percentage of sulfur in the impure sample = (mass of sulfur / mass of impure sample) * 100
= (64.12 g/mol / 233.39 g/mol) * 100
= 27.46%
To calculate the percentage purity of the salt, we use the mass of the BaSO4 precipitate and assume that all the sulfur in the impure sample was converted to BaSO4.
Percentage purity of salt = (mass of BaSO4 precipitate / mass of impure sample) * 100
= (2.496 g / 1.562 g) * 100
= 159.78%
Note: The percentage purity can exceed 100% in cases where the impurity adds to the weight of the sample.
To calculate the percentage of sulfur (%S) in the sample, you need to determine the amount of sulfur in the BaSO4 precipitate. Since the molecular weight of BaSO4 is 233.39 g/mol and the molecular weight of sulfur (S) is 32.07 g/mol, you can use these values to determine the amount of sulfur in the precipitate.
1. Calculate the amount of sulfur in the BaSO4 precipitate:
Sulfur amount = (mass of BaSO4 precipitate) × (molar mass of S) / (molar mass of BaSO4)
= 2.496 g × (32.07 g/mol) / (233.39 g/mol)
= 0.342 g
2. Calculate the percentage of sulfur in the sample:
%S = (amount of sulfur in precipitate) / (mass of sample) × 100
= 0.342 g / 1.562 g × 100
= 21.92%
To calculate the percentage purity of the salt, you need to determine the amount of sodium sulfate (Na2SO4) in the impure sample and calculate the percentage of that amount in relation to the total sample weight.
3. Calculate the amount of sodium sulfate in the impure sample:
Sodium sulfate amount = (mass of impure sample) - (mass of BaSO4 precipitate)
= 1.562 g - 2.496 g (since BaSO4 includes sulfur from Na2SO4)
= -0.934 g
Note: The negative value suggests that the BaSO4 precipitate contains more sulfur than it should from the sodium sulfate. This indicates an impurity in the sample.
4. Calculate the percentage purity of the salt:
%Purity = (Na2SO4 amount) / (mass of impure sample) × 100
= (-0.934 g) / 1.562 g × 100
= -59.76%
As the percentage purity is negative, it means that the impure sample contains less Na2SO4 than it should, indicating the presence of impurities.