Compute the boiling point elevation of a salt water solution that contains 2.60 g of NaCl dissolved in 121 ml of water. Enter the number of degrees celsius that the boiling point will be elevated.
moles NaCl = grams NaCl/molar mass NaCl
Solve for moles NaCl.
molality = #moles/kg solvent.
Solve for molality.
delta T = i*Kb*m
Solve for delta T
Note:i is the van't Hoff factor. It is 2 for NaCl.
To compute the boiling point elevation, we can use the formula:
ΔTb = Kb * m
Where:
ΔTb = boiling point elevation
Kb = molal boiling point constant of the solvent
m = molality of the solute
First, we need to find the molality of the NaCl solution.
Molality (m) is calculated by dividing the moles of solute by the mass of the solvent in kilograms.
1. Calculate the moles of NaCl:
We know that the molar mass of NaCl is approximately 58.44 g/mol.
By dividing the given mass (2.60 g) by the molar mass, we can find the moles of NaCl in the solution.
moles of NaCl = mass of NaCl / molar mass of NaCl
= 2.60 g / 58.44 g/mol
2. Convert the volume of water from milliliters to kilograms:
Since the density of water is 1 g/ml, we can assume that the mass of 121 ml of water is equal to 121 g.
To convert grams to kilograms, we divide by 1000.
mass of water = 121 g / 1000
= 0.121 kg
3. Calculate the molality of the solution:
Using the moles of NaCl and the mass of water in kilograms, we can compute the molality.
molality (m) = moles of NaCl / mass of water (kg)
4. Lookup the molal boiling point constant of water (Kb):
The molal boiling point constant of water is approximately 0.512 °C/m.
5. Calculate the boiling point elevation (ΔTb):
Using the molal boiling point constant and the molality, we can calculate the boiling point elevation.
ΔTb = Kb * m
Now, let's put these values into the formula:
ΔTb = 0.512 °C/m * molality
Substituting the value of the molality we calculated earlier:
ΔTb = 0.512 °C/m * (moles of NaCl / mass of water (kg))
Calculate the values on the right side of the equation and multiply:
ΔTb = 0.512 °C/m * (moles of NaCl / mass of water (kg))
Finally, we have the boiling point elevation (ΔTb) in degrees Celsius.