1) H₂

Step One: the molar mass of H₂ is 2.016 g/mol

Step Two: 2.016 g/mol ÷ 6.022 x 10²³ mol¯¹ = 3.348 x 10¯²⁴ g

2) PCl₅

Step One: the molar mass of PCl₅ is 208.239 g/mol

Step Two: 208.239 g/mol ÷ 6.022 x 10²³ mol¯¹ = 3.458 x 10¯²² g

3) UF₆

Step One: the molar mass of UF₆ is 352.019 g/mol

Step Two: 352.019 g/mol ÷ 6.022 x 10²³ mol¯¹ = 5.846 x 10¯²² g

Step One: the molar mass of F₂ is 37.997 g/mol

Step Two: 37.997 g/mol ÷ 6.022 x 10²³ mol¯¹ = 6.310 x 10¯²³ g

Step One: the molar mass of CH₄ is 16.043 g/mol

Step Two: 16.043 g/mol ÷ 6.022 x 10²³ mol¯¹ = 2.664 x 10¯²³ g

You may have noticed the use of the unit mol¯¹ on Avogadro's Number. This unit means "1/mol" or "per mole." The numerator label is not written because it is (usually) unimportant if we are discussing atoms, molecules, ions, or whatever. In addition, the contxt often supplies what the numerator should be. In the cases above, it would be "molecule."

It also may be important for you to satisfy yourself that the units of "mol" do, in fact, cancel. Return Some Additional Problems