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

4) F2

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

5) CH4

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