# Chemistry

7) 14 carat gold has a purity of 58.3%. How many moles of gold are in 163 grams of 14 carat gold?
8) A 15.9 g sample of iron ore is treated as follows. The iron in the sample is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 11.5 g. What was the mass of iron in the sample of ore?
9) A 47.2 g of iron ore is treated as follows. The iron in the sample is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 13 grams. What was the percent iron in the sample of ore?
10) An ore contains Fe3O4 and no other iron. The iron in a 51.5-gram sample of the ore is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 22.3 g. What was the mass of Fe3O4 in the sample of ore?

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1. 7) 14 carat gold has a purity of 58.3%. How many moles of gold are in 163 grams of 14 carat gold?
g Au = 163 x 0.583 = ?
mols Au = g/atomic mass = ?

8) A 15.9 g sample of iron ore is treated as follows. The iron in the sample is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 11.5 g. What was the mass of iron in the sample of ore?
11.5 g Fe2O3 x (2*atomic mass Fe/molar mass Fe2O3) = ?

9) A 47.2 g sample of iron ore is treated as follows. The iron in the sample is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 13 grams. What was the percent iron in the sample of ore?
Follow the above to find grams Fe in the sample. Then % Fe = (g Fe/mass sample)*100 = ?

10) An ore contains Fe3O4 and no other iron. The iron in a 51.5-gram sample of the ore is all converted by a series of chemical reactions to Fe2O3. The mass of Fe2O3 is measured to be 22.3 g. What was the mass of Fe3O4 in the sample of ore?
Follow same procedure as #8. The factor to use is (2*molar mass Fe3O4/3*molar mass Fe2O3)

Post your work if you have further questions.

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