Final answer:
Without the balanced chemical equation for the reaction of Sb2S3 with Fe, it is impossible to determine the mass of the product formed.
Step-by-step explanation:
To determine the mass of the product formed from the reaction of 12 grams of Sb2S3 with 13 grams of Fe, one would need to know the balanced chemical equation for the reaction. Without the chemical equation, it's impossible to calculate the stoichiometry and thereby ascertain the mass of the product formed. The question as posed does not provide sufficient information to answer it correctly. Since we cannot provide an accurate answer due to insufficient data, we will not attempt to infer any potential reaction products or their masses.