1.) A 3.000gram sample of a hydrate compound containing Co, C2O4, and H2O was combusted to give 1.316g of Co3O4. What is the percentage of Cobalt in the oxide?
3.) 2.000 grams of a sample containing Co, C2O4, and H2O showed there to be 0.9621g of oxalate in the sample. Was is the percentage of oxalate in 3.000grams of that sample?
What is the percentage of water in the sample for problems 1 to 3?
A.
%Co in Co3O4 = (3*atomic mass Co/molar mass Co3O4)*100 = ? You should get about 72% but get closer than that. How many grams Co is there in that sample? That is 0.7242 x 1.316g = about 0.95 g which means you must have started with 0.95 g Co in the 3.000 g sample of the hydrate.
The 2.000 g sample contained 0.9621g C2O4 which is 0.9621/2.000)*100 = about 48%. Again, you get closer than that.You want to know how much is in a 3.00 g sample. %C2O4 x 3.00 = about 1.44 g C2O4 in the initial 3.00 g sample.
So how much H2O is there? That is 3.00 g - 1.44g C2O4 - 0.95g Co = about 0.61g so %H2O = about (0.61/3.00)*100 = about 20%.
The problem doesn't ask for it but you can determine the empirical formula from these numbers. I won't do it here but the empirical formula is CoC2O4.2H2O. Post your work if you get stuck.
To determine the percentage of cobalt in the oxide and the percentage of oxalate in the sample, we need to use the concept of stoichiometry. Here are the steps to solve each problem:
1.) Percentage of Cobalt in Co3O4:
First, calculate the moles of Co3O4 using the given mass and molar mass of Co3O4 (342.46 g/mol). The moles of Co3O4 can be found by dividing the mass by the molar mass:
Moles of Co3O4 = Mass of Co3O4 / Molar mass of Co3O4
Next, determine the moles of cobalt in Co3O4. Since the ratio of cobalt to Co3O4 is 3:1, multiply the moles of Co3O4 by the ratio:
Moles of Cobalt = Moles of Co3O4 * (3 moles of Cobalt / 1 mole of Co3O4)
Finally, calculate the percentage of Cobalt in Co3O4 by dividing the moles of cobalt by the molar mass of Co3O4 and multiplying by 100:
Percentage of Cobalt = (Moles of Cobalt * Molar mass of Cobalt) / Mass of Co3O4 * 100
2.) Percentage of Oxalate in the Sample:
Start by calculating the moles of oxalate using the given mass and the molar mass of oxalate (88.02 g/mol):
Moles of Oxalate = Mass of Oxalate / Molar mass of Oxalate
Next, calculate the percentage of Oxalate in the sample by dividing the moles of oxalate by the mass of the sample and multiplying by 100:
Percentage of Oxalate = (Moles of Oxalate / Mass of Sample) * 100
3.) Percentage of Water in the Sample:
To find the percentage of water in the sample, subtract the sum of the percentages of cobalt and oxalate from 100%:
Percentage of Water = 100% - (Percentage of Cobalt + Percentage of Oxalate)
By following these steps, you can determine the percentage of cobalt, oxalate, and water in the given samples.