In: Chemistry
The molality of pure water is _____
(a) 55.5
(b) 50.5
(c) 18
(d) 60.5
Answer : a) 55.5 moles/kg
Explanation :
Step 1 :
For a pure water the density is 1 gm/cc. In other words the mass is equal to the volume.
Density (gm/cc) = mass (gm)/ Volume (cc)
i.e 1 (gm/cc) = 1(gm) / 1 (cc)
i.e 1 Kg = 1000 gm
Step 2 :
no.of moles of pure water
n = 1000/18
Molality (m) = Number of moles/kg of solvent
m = 55.55/ kg of solvent
m = 55.5 moles/kg
a) 55.5