Question

Question #f79bb

Answer 1

In order to calculate the mass of 2.1 moles of acetylene, you must first determine the mass of one mole, which is its molar mass. The mass of one mole of a substance is its atomic weight in grams/mole (g/mol). Then multiply the molar mass times the number of moles given in the question.

To determine the molar mass of `"C"_2"H"_2`, multiply the atomic weights as g/mol for carbon and oxygen times the number of atoms of each element in the compound, then add them together.

Molar mass of `"C"_2"H"_2`.

C: 12.011g/mol x 2 = 24.022g/mol

H: 1.008g/mol x 2 = 2.016g/mol

Total: 26.038g/mol

Molar mass of `"C"_2"H"_2` is 26.038g/mol

Calculate the mass of 2.1 mol `"C"_2"H"_2`.

`"2.1 mol C"_2"H"_2` x `"26.038g"/"1 mol"` = `"54.6798g/mol"`

The mass of 2.1 moles `"C"_2"H"_2` is 54.6798g, which is rounded to 55g to match the least number of significant figures, which is two in 2.1 moles.