Răspuns:
Masa moleculara a NaOH = 23 +16 +1=40 Consideram 40 ……………………..100%
23 ……………………….x%
16………………………y%
1………………………..z%
De aici scoatem fiecare necunosctuta astfel: X=23*100/40=57,5% Na Y=16*100/40=40%O Z=1*100/40=2,5%H
La fel facem si pt Ca(OH)2 Masa molecular: 23+2*(16+1)=57 57…………………………….100% 23……………………………..x% 2*16…………………………y% 2*1……………………………z% X=(23*100)/57=40,35 % Ca Y=(2*16*100)/57=56,14%O Z=(2*1*100/57)=3,50%H
Al(OH)3=hidroxid de aluminiu masa molară:A(Al)+3A(O)+3A(H) M=27+3•16+3•1=78g/mol 78g
Al(OH)3........27g Al......48g O.......3g H 100g Al(OH)3....... X g Al......Y g O.......Z g H =>X=34,61% Al Y=61,53% O Z=3,86% H A(..)=masa atomica M=masa molară