Answer :
(a) The number of sulfur atoms are,  .
.
(b) The mass of the mass of  is, 1059.682 grams.
 is, 1059.682 grams.
(c) The number of moles of  is,
 is, 
(d) The mass of the mass of  is,
 is, 
Explanation :
(a) As we are given the number of moles of  is, 1.75 mole. Now we have to calculate the number of sulfur atoms.
 is, 1.75 mole. Now we have to calculate the number of sulfur atoms.
In the  , there are 2 iron atoms, 3 sulfur atoms, 12 oxygen atoms.
, there are 2 iron atoms, 3 sulfur atoms, 12 oxygen atoms.
As, 1 mole of  contains
 contains  number of sulfur atoms.
 number of sulfur atoms.
So, 1.75 mole of  contains
 contains  number of sulfur atoms.
 number of sulfur atoms.
The number of sulfur atoms are, 
(b) As we are given the number of moles of  is, 2.65 mole. Now we have to calculate the mass of
 is, 2.65 mole. Now we have to calculate the mass of  .
.

The molar mass of  = 399.88 g/mole
 = 399.88 g/mole

The mass of the mass of  is, 1059.682 grams.
 is, 1059.682 grams.
(c) As we are given the mass of  is, 3.45 grams. Now we have to calculate the moles of
 is, 3.45 grams. Now we have to calculate the moles of  .
.

The molar mass of  = 399.88 g/mole
 = 399.88 g/mole


The number of moles of  is,
 is, 
(d) As we are given the formula unit of  is, 3. Now we have to calculate the mass of
 is, 3. Now we have to calculate the mass of  .
.
As we know that 1 mole of  contains
 contains  formula unit.
 formula unit.
Formula used :



Now we have to calculate the mass of  .
.

The molar mass of  = 399.88 g/mole
 = 399.88 g/mole

The mass of the mass of  is,
 is, 