Saved Bookmarks
| 1. |
Aqueoussolutionof NaOH ismarked10%(w//w). Thedensityof thesolutionis 1.070 g cm^(-3). Calculate (i) molarity and (ii)molalityof NaOH. |
|
Answer» Densityof NaOHsolution =D =1.070 G `CM^(-3)` Molarmass ofNaOH=40 g `mol^(-1)` (i) Molarity of NaOHsolution = ? (ii)Molalityof NaOHsolution = ? (i) Formolarityof solution: Consider 100 gNaOHsolution `:. ` Weight `H_(2)O+` Weightof NaOH =100 g `:. ` Weightof `H_(2)O = 100 - 10= 90 g` Numberof molesof NaOH`= (W_(NaOH))/(M_(NaOH))` `:. n_(NaOH) = .(10)/(40)` `=0.25 `mol Densityof solution `(D) = ("Weight of solution" )/(" volumeof solution " ) = (W)/(V)` `:.V = (W)/(D)` `=(100)/(1.070)` `=93 . 46 cm^(3)` `=0.09346 dm^(3)` Molarity`=(n)/(V)= (0.25)/(0.09346) =2.675 "mol"dm^(-3)(or M)` (ii) For molalityof NaOHsolution : Molality`=("MOLAR of NaOH ") /("Mass ofsolventin gram ") xx 1000` `=(0.25)/(90) xx 1000` `=2.779"mol" kg^(-1)(or m)` |
|