Question

1. How many ATOMS of sulfur are present in 4.77 moles of disulfur decafluoride? atoms of sulfur. 2. How many MOLES of fluorine are present in 1.05x1021 molecules of disulfur decafluoride? moles of fluorine.

Answer 1

1) Dusulfur decafluoride is S2 F10

From the formula we can see one molecule has 2 sulfur atoms.

OR

one mole of S2F10 has 2 moles of S atoms

Thus 4.77 moles of S2F10 has 2 x4.77 = 9.54 moles of S atoms.

We know one mole of any substance contains 6.02x1023 such particles.

So atoms of S in 9.54 moles= moles x Avogadro number

= 9.54 x 6.02x1023

=5.743x1024

Q2)similarly

one mole of S2F10 has 6.02 x 1023 molecules and has 10x 6.02 x 1023 fluorine atoms.

But we have  

1.05x1021   molecules of S2F10

moles off S2F10 = given molecules/Avogadro number = 1.05x1021 / 6.02 x 1023 =1.744 x10-3 moles

thus

one mole of S2F10 has 10 moles of F atoms

1.744 x10-3 moles of S2F10 has  1.744 x10-3 moles x 10 /1 = 1.744 x10-2 moles of F atoms.

If moles of difluorine are required = moles of F atoms/2 = 8.72x10-3 moles of F2 molecules