Mass fraction of iron in a mixture of iron and copper filings is 30%. What mass of copper can be isolated from 150 g of the mixture?

Given:
ω (Fe) = 30%
m mixture (Fe, Cu) = 150 g
Find: m (Fe) -?
Decision:
1) Calculate the mass fraction of Cu in the mixture:
ω (Cu) = 100% – ω (Fe) = 100% – 30% = 70%;
2) Calculate the mass of Cu that can be isolated from the mixture:
m (Cu) = ω (Cu) * m mixture (Fe, Cu) / 100% = 70% * 150/100% = 105 g.
Answer: Cu mass is 105 g.