7, 2g of sodium carbonate, Na2Co3.nH2O is strongly heated and a residue of 2.7g are produced..... Calculate the nber of moles of water

Answer 1

2.7/molmassNa2O=2.7/62 = molesNa2O

so you have that number of moles also of Na2CO3.nH20

formula mass Na2CO3.nH20 *moles=mass

or formulamass=7.2/(2.7/62)
=165

so 165=2.7(46+12+48+n18)
or 2.7*18n=165-(2.7*106)
n=2.5

check my math. I was expecting 5.