Hello. My next (and this year's first) experiment will be to determine the apparent molar volume of NaCl.
And as I started preparing for it, I ran across a problem.
The empirical equation that describes the behaviour of a diluted salt solution is
where V
B is the apparent partial molar volume of component B
m
B is the molality of that component in mol(B)/kg
V
B0 is the apparent partial molar volume of component B for an infinitely diluted solution
a is a constant
We can also calculate the apparent volume by
where V is the volume of the solution
V
A is the volume of solvent
n
B is the amount of substance B (solute)
According to my handbook, the numerical value of n
B is equal to the molality, because molality is defined as the amount of substance B divided by the mass (1kg) of the solvent. So, the book says, n
B and m
B are (somehow) interchangeable and the the volumes V and V
A are expressed as
and
replacing these two in the second equation I should get
Now, my question is: Can you really just substitute the amount of B (n
B) with molality (m
B)?
And in
, where did the m
B come from? Because, if i multiply molality(m
B) with molar mass(M
B), don't I get just a number, with no unit? - ([mol/kg] * [kg/mol] = 0 )