I was wondering if I could post a rather difficult Stoichiometry problem. It involves the combustion of three different hydrated salts: Na2CO3.10H2O, MgSO4.7H2O and CuSO4.5H2O:
You are given a mass of three hydrated salts: (see above). The total mass of the mixture is 12.123 grams. When the mixture is gently heated, the following two reactions occur:
Na2CO3.10H2O (s) + _______________> Na2CO3.7H2O (s) +3H2O (g)
MgSO4.7H2O (s) ______________> MgSO4.H2O (s) +6H2O (g)
After these reactions are complete, the mass of the mixture has decreased to 9.049 grams. This mixture is then heated more strongly and the following additional reactions occur:
Na2CO3.7H2O (s) ___________________> Na2CO3 (s) + 7H2O
MgSO4.H2O (s) _____________________> MgSO4 (s) + H2O (g)
CuSO4.5H2O (s) _____________________> CuSO4 (s) + 5H2O (g)
After this final heating, the mass of the mixture has decreased to 6.412 grams. From this information, calculate the masses of each of the three compounds in the original mixture.
ANSWERS GIVEN: 1.374 grams of Na2CO3,.10H2O, 6.418 grams of MgSO4.7H2O and 4.331 grams of CuSO4.5H2O. I did calculate the Molecular Weights of each one of these compounds at every different stage of the reactions. Then I tried to calculate how much water was lost at each stage, but my answers are not the same.
Any ideas out there? I know a lot of Chemists and Chemical engineers peruse this site on a regular basis. I figured this would be the place to go, rather than Yahoo Answers, for a question this difficult.