Convert 4.58 x 10^23 formula units sodium sulfate to grams

Answer 1

Hello, Alli,

The question wants us to convert 4.58 x 10²³ "formula units" into grams. Formula units can be read as "molecules." We need a conversion factor that converts molecules into grams. We'll need two, actually.

The first step is to convert molecules into moles. Avogadro's number is the information we need, since:

6.02 x 10²³ molecules = 1 mole

Make this into a conversion factor by dividing one side by the other. In this case I'll divide moles by molecules:

1 = (1 mole)/(6.02x10²³ molecules)

Since this is equal to 1, we can multiply it times the number of sodium sulfate molecules to yield moles sodium sulfate.

(4.58x10²³ molecules Na₂SO4)*(1 mole Na₂SO4)/(6.02x10²³ molecules Na₂SO4)

The unit molecules Na₂SO4 cancel, leaving moles Na₂SO4.

0.761 moles Na₂SO4

Then we need to convert moles Na₂SO4 to grams Na₂SO4. Find the molar mass of Na₂SO4.

I get 142 (grams Na₂SO4/mole Na₂SO4)

Multiply that times the moles Na₂SO4 so that moles Na₂SO4 cancel, leaving grams Na₂SO4.

I get 108 grams Na₂SO4. Does this sound about right? Well, we can see that the number of molecules of Na₂SO4 is less than the number needed to make a full mole. We also see that 1 mole should have a mass of 142 grams, so we should be under that amount, which 108 grams is.

I hope this helps,

Bob