What is the mass in grams of 0.5 moles of Na2SO4? How many moles of water are contained in 50.0 g of H2O?

Question

What is the mass in grams of 0.5 moles of Na2SO4? How many moles of water are contained in 50.0 g of H2O?

Answer 1

1 mole of an atom weighs the atomic mass number of that atom.

1 mole of a molecule weighs the atomic mass number of the molecule

For NA2S04, the atomic mass number is

2(22.98977)sodium+1(32.065)sulfer+4(15... oxygen

= 142.02 grams.  Half a mole would have half that mass or 71.01 grams

Now 1 mole of water weighs 18.01528 grams so

50 grams = 50 grams (1mole/18.0528 grams) =2.775 moles of water in 50 grams

Answer 2

the equation for this is

m=Mxn

so the molar mass of Na2S04

2(22.99)+142.08g/mol

45.98+142.08

188.06g/mol

m=188.06x0.5

94.03g

n=

m

M

H =2(1.01)g/mol

O=2(16.00)g/mol

2.02+32 = 34.02g/mol

so

50.0g divided by 34.02g/mol

1.50moles

hope i helped!