According to its chemical formula, ferrous fumarate is known to be composed of four elements. The relative molecular mass of C4H2FeO4 is 170, so its molar mass is 170g/mol. 1mol contains 6.02× 1023 molecules in any substance, and one molecule of ferrous fumarate contains two hydrogen atoms, so 0.05mol of ferrous fumarate contains 0./kloc.

Ferrous fumarate molecule.

So the answer is: 4; 170g/mol; 3.0 1× 1022.