Respostas

2014-04-06T18:09:39-03:00
H2O H=1X2=2
        O=16X1=16
                   18g/mol
18g-1mol
90g-x
18x=90
x=5mol
3 4 3
2014-04-06T19:43:00-03:00
18u > 18g > 1 mol > 6.02 x 10^23

18g --- 1 mol
90g --- x

x= 1.90  / 19 = 90/18 = 5 mols
1 4 1