Final answer:
To identify the iron(II) salt, the mass percent of iron in the experimental sample was calculated and compared with the theoretical values for iron(II) iodate, iron(II) phosphate, and iron(II) acetate. The salt with a mass percent closest to the experimentally determined value was iron(II) phosphate.
Step-by-step explanation:
The student is trying to identify which iron(II) salt they have from a choice of iron(II) iodate (Fe(IO₃)₂), iron(II) phosphate, or iron(II) acetate (Fe(C₂H₃O₂)₂) by determining the mass percentage of iron in the sample. Since they found that their sample contains 0.600 g of iron out of 1.28 g total mass of salt, we can calculate the mass percentage of iron as follows:
Mass percent of iron = (mass of iron / total mass of salt) × 100
Mass percent of iron = (0.600 g / 1.28 g) × 100 = 46.875%
We need to compare this to the theoretical mass percent of iron in each of the potential salts:
- Iron(II) iodate: Fe(IO₃)₂ - The molar mass of Fe(IO₃)₂ is approximately 389.71 g/mol and iron's molar mass is 55.845 g/mol. The theoretical mass percent of Fe in Fe(IO₃)₂ would be (55.845 g/mol / 389.71 g/mol) × 100 = 14.32%.
- Iron(II) phosphate: Fe₃(PO₄)₂ - The molar mass of Fe₃(PO₄)₂ is approximately 357.48 g/mol for iron alone (since there are 3 moles of Fe) and iron's molar mass is 167.535 g/mol. The theoretical mass percent of Fe in Fe₃(PO₄)₂ would be (167.535 g/mol / 357.48 g/mol) × 100 = 46.87%.
- Iron(II) acetate: Fe(C₂H₃O₂)₂ - The molar mass of Fe(C₂H₃O₂)₂ is approximately 173.71 g/mol and iron's molar mass is 55.845 g/mol. The theoretical mass percent of Fe in Fe(C₂H₃O₂)₂ would be (55.845 g/mol / 173.71 g/mol) × 100 = 32.15%.
The salt with a mass percentage closest to the experimental value of 46.875% is iron(II) phosphate. Therefore, the unidentified salt is iron(II) phosphate.