100 tons of hard lead (98%Pb, 2%Sb) are melted in a steel kettle and then treated with 2 tons of PbO. The products are (1) a slag consisting of PbO and Sb2O3, analyzing 20%Sb, (2) a Pb- Sb alloy of lowered Sb content and negligible oxygen content. Calculate the % Sb in the final alloy. The reaction involved is:
3PbO + 2Sb(in Pb) = Sb2O3 +3 Pb