Kemolalan suatu larutan 25% berat etanol C2H50H (mr 46) ...

% ---> Berat ( gram )

25% --> 25g
Kalau larutan 25 gram , maka air = 75 gram

m = g/mr × 1000/p
m = 25/46 × 1000/75
m = 25000/3450
m = 7,24 molal

% m/m C2H5OH = 25%

Asumsikan :
m total = 100 gram
m C2H5OH = 25% × m total
= 25% × 100 gram
= 25 gram

% air = 100% - % C2H5OH
= 100% - 25%
= 75%

m air = 75% × m total
= 75% × 100 gram
= 75 gram

Mr C2H5OH = 46

Kemolalan C2H5OH
m = ( m C2H5OH / Mr ) × ( 1000 / m air )
m = ( 25 gram / 46 ) × ( 1000 / 75 )
m = 7,2464 molal