Consider the balanced equation: Na2SO4 + 2C  = Na2S + 2CO2.
How many grams of Carbon will be consumed when 5.00g Na2SO4 react?

Hi!!

The balanced equation tell us that 2 moles of Carbon will be consumed
per 1 mol of Na2SO4 to form 1 mol of Na2S and 2 moles of CO2.

The sum of the atomic weights of all the atoms in a molecule of a
substance indicates us the weight of 1 mol of such substance.

Atomic weights:
Na = 22.99g
S  = 32.07g
O  = 16.00g
C  = 12.01g

1 mol of Na2SO4 will weight:
2*(22.99g) + 32.07g + 4*16.00g = 142.05g

2 mol of C will weight 
2*12.01g = 24.02g

1 mol of Na2SO4 will react with 2 moles of C, 
then:
142.05g of Na2SO4 will react with 24.02g of C, 
then:
5.00g of Na2SO4 will react with (5.00*24.02/142.05)g = 0.845g of C .


I hope that this helps you. feel free to request for a clarification
if you need it.

Regards.
livioflores-ga

This person thoroughly explained my question and helped me to
understand it. It was much needed help since I don't have anyone to
help me with this subject.