urgent Chemistry help ! Please and Thanks!?

health nut · #1 (**permalink**) 04-29-2008, 11:22 PM

I have lab and i'm really confused with the questions.Here is the data:

mass of small container and cover: 29.1 g

Mass of small container, cover and
MgSO4 hydrate: 34.1g

Mass of small container, cover and
anhydrous MgSO4: 31.9g

The mass of anhydrous MgSO4 is 2.5g

How would i calculate the moles anhydrous MgSO4 ???

The mass of the water driven off is 2.5g

How would I calculate the moles of water driven off???

cstspeedy · #2 (**permalink**) 04-29-2008, 11:24 PM

Moles of anhydrous MgSO4 is the number of grams divided by the molecular mass:

2.5g / (24.3 + 32.1 + 64.0) = 2.5 / 120.4 = 0.0208 moles

The moles of water driven off is the mass of water driven off divided by the molecular mass of water:

2.5 / 18.0 = 0.139 moles

Round to the correct number of significant figures.

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