Post Lab Questions 1) How would your calculation of the average number of water
ID: 849687 • Letter: P
Question
Post Lab Questions
1) How would your calculation of the average number of water molecules present in Epsom salt be affected
if you heated your sample too strongly and and too long and decomposition started to take place? (Too
High, Too Low, Unchanged) Explain
2) How would the calculated number of water molecules present in Epsom salt be affected if procedure was
changed so the analysis was preformed using 8.500g of hydrated salt instead of 1.500g? (Too High, Too
Low, Unchanged) Explain
3) Calculate the mass percent of water contained in a sample of MgSO4.7H2O?
4) A sample of raw mining ore contains a hydrated salt called copper sulfate pentahydrate, CuSO4.5H2O. If
a 10.000g of the ore loses 0.499g of water when heated strongly, what is the mass percentage of
CuSO4.5H2O in the raw ore sample?
Explanation / Answer
1) Too high.
Because Epsom salt is: MgSO4 7H2O, and heating about 5 mints will evaporate water. However, too strongly and too long time heating causes it to decompose to magnesium oxide and sulfur trioxide. If the mass and moles of water were unchanged, but the mass and moles of MgSO4 will be decreased. Therefore, the ratio of H2O to MgSO4 will be increased, and the average number of water molecules present in Epsom salt will be too high.
2)
Mg = 24.31 g/mol, S = 32.07 g/mol, O = 16.00 g/mol, H = 1.008
The mass of 1 mol of MgSO4