Freezing point of pure water = -2, Freezing point of Unknown solution = -1
Mass of unknown in 50g of water = 1.9964g. Calculate the delta T for the solution of the unknown solid and determine the molecular weight of the unknown solid.
Freezing point is supposed to go down. It went up. Bad data. Means nothing to me.
If it had gone down then how would we calculate it
delta T = Kf*m
Substitute for delta T and Kf and solve for m = molality
In your case delta T is +1 and kg solvent is 0.050.
m = mols/kg solent
You have m and kg solvent; solve for mols.
mol = grams/molar mass. You have mol and grams, solve for molar mass.
To calculate the delta T for the solution and determine the molecular weight of the unknown solid, we need to use the formula:
ΔT = Kf * m
where:
- ΔT is the change in freezing point
- Kf is the cryoscopic constant of the solvent (water in this case)
- m is the molality of the solution
First, let's calculate ΔT:
ΔT = Freezing point of pure water - Freezing point of unknown solution
= -2°C - (-1°C)
= -1°C
Now, we need to calculate the molality (m). Molality is defined as the moles of the solute divided by the mass of the solvent (in kg).
moles of solute = mass of unknown solid / molar mass of unknown solid
Given that the mass of the unknown solid is 1.9964g, we need to convert it to kg:
mass of unknown solid = 1.9964g = 0.0019964kg
Next, we need to determine the number of moles of the unknown solid. To do this, we'll need to calculate the molar mass of the unknown solid.
molar mass = mass of unknown solid / moles of unknown solid
To find the moles of the unknown solid, we can use the formula:
moles of unknown solid = mass of unknown solid / molar mass of unknown solid
Since we are given the mass, we need to solve for the molar mass:
molar mass of unknown solid = mass of unknown solid / moles of unknown solid
Substituting the known values:
molar mass of unknown solid = 0.0019964kg / moles of unknown solid
We can rearrange this equation to solve for moles of unknown solid:
moles of unknown solid = 0.0019964kg / molar mass of unknown solid
Now, we can substitute the value of moles of unknown solid into the formula:
m = moles of solute / mass of solvent
m = moles of unknown solid / mass of water
The mass of water is given as 50g, which we also need to convert to kg:
mass of water = 50g = 0.05kg
Now, we can calculate the molality:
m = (0.0019964kg / molar mass of unknown solid) / 0.05kg
= 0.039928kg / molar mass of unknown solid
Substituting the value of ΔT and molality into the formula:
ΔT = Kf * m
-1°C = Kf * (0.039928kg / molar mass of unknown solid)
Now, we can rearrange the equation to solve for the molar mass of the unknown solid:
molar mass of unknown solid = Kf * (0.039928kg / -1°C)
The Kf value for water is 1.86 °C·kg/mol. Let's substitute that value:
molar mass of unknown solid = 1.86 °C·kg/mol * (0.039928kg / -1°C)
Simplifying the equation:
molar mass of unknown solid = -1.86 °C·kg/mol * 0.039928kg
And finally, calculating the molar mass of the unknown solid:
molar mass of unknown solid = -0.07412 kg·°C/mol
However, it appears that there is an inconsistency in the given data, as a negative molar mass is not physically meaningful. Please double-check the provided information to ensure the accuracy of the given values.