Question

4gram of NaoH is contain in decilitre of solution calculate the following 1. Mole fraction of NaoH 2. Molality of NaoH 3. molarity of NaoH ( density of NaoH is 1.038 pergm cm³

Answer 1

4 gram of naoh is contain in deciliter of /1.038

Answer 2

Gram molecular weight of NaOH = 40 gm

Thus, 4 gm NaOH = 4/40 moles of NaOH = 0.1 moles of NaOH

1 decilitre = 1/10 litre = 0.1 litre

So, in 0.1 litre there is 0.1 moles of NaOH

Thus, in 1 litre there will be = 0.1/0.1 = 1 mole NaOH

Therefore, the solution is 1 molar.

Now, density = (mass/volume)

Given, density= 1.038 gm/cm³ and volume= (1/10) litre

Now, 1 litre = 1000 cm³

Mass of the solution = 1.038 X 1/10 X 1000 = 103.8 gm

Mass of solvent = (103.8 - 4) gm = 99.8 gm

99.8 gm solvent contains 0.1 moles of NaOH

Thus, 1000 gm solvent will contain = [(0.1 X 1000)/99.8] moles of NaOH = 1.002 moles of NaOH

Therefore, the solution is 1.002 molal.    

Moles of water present = (99.8/18) = 5.54

Thus the mole fraction of NaOH = 0.1/(0.1+5.54) = 0.018