Elemental sulfur occurs as octatomic molecules, #S_8#. What mass (g) of fluorine gas is needed to react completely with 17.8 grams of sulfur to form sulfur hexafluoride?

1 Answer
Meave60
Feb 21, 2016

#"63.2 g F"_2"# are needed to react completely with #"17.8 g S"_8"# to produce #"SF"_6"#.

Explanation:

Start with a balanced equation.

#"S"_8+"24F"_2##rarr##"8SF"_6"#

Then determine the molar masses of #"S"_8"# and #"F"_2"# by multiplying the subscript of each element by its atomic mass from the periodic table in g/mol.

#"S"_8":# #(8xx32.06 "g/mol")="256.48 g/mol"#
#"F"_2":# #(2xx18.998 "g/mol")="37.996 g/mol"#

Determine the mass of #"F"_2"# needed to react completely with #"S"_8"# to form #"SF"_6"#.

  1. Divide the given mass #"S"_8"# by its molar mass.
  2. Multiply the mole ratio between #"F"_2"# and #"S"_8"# from the balanced equation with the moles #"F"_2"# in the numerator: #(24"mol F"_2)/(1"mol S"_8)#
  3. Multiply moles #"F"_2"# times its molar mass to get grams #"F"_2"#.

#17.8cancel"g S"_8xx(1cancel"mol S"_8)/(256.48cancel"g S"_8)xx(24cancel"mol F"_2)/(1cancel"mol S"_8)xx(37.996"g F"_2)/(1cancel"mol F"_2)="63.2 g F"_2# rounded to three significant figures

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