Astudent heats 2.796g of zinc powder with 2.414g of sulphur. he reported that he obtained 4.169g of zinc sulfide and recover 1.041g of unreacted sulfur.
show by calculation whether or not his results obey the law of conversation of mass

The mass of reactants and products are equal hence the reaction obeys law of conservation of mass

Explanation:

The law of mass conservation states that for a closed system to all transfer of mass, the mass of system must remain constant over time. This means for a chemical reaction, the mass of reactants must equal the mass of products.

if 2.796g of Zn reacts with 2.414g of sulphur to produce 4.169g of ZnS ad 1.041g of unreacted sulphur, then it means that accorfing to the law of mass conservation, the mass of reactants (zinc and sulphur), must be equal to mass of products (zinc sulfide and unreacted sulphur)

Mass of reactants = 2.796g + 2.414g =5.21g

Mass of products = 4.169g + 1.041g=5.21g

the answer is 75.0%.