What is the boiling point of a solution composed of 15.0g urea, (NH2)2CO, in .500kg of water?
moles = grams/molar mass
Sole for moles.
molality = moles/kg solvent.
Solve for molality
delta T = Kb*m
solve for delta T, then add to 100 to find the b.p.
50
To find the boiling point of a solution, you can use the equation known as the boiling point elevation equation: ΔTb = Kbm.
Where:
ΔTb = boiling point elevation
Kb = molal boiling point elevation constant
m = molality of the solution
The boiling point elevation constant for water is approximately 0.512 °C/m.
To solve this problem, we need to find the molality of the solution first.
Step 1: Calculate the number of moles of urea:
Given: mass of urea = 15.0 g
Molar mass of urea = 60.06 g/mol
Number of moles = mass / molar mass
Number of moles = 15.0 g / 60.06 g/mol
Step 2: Calculate the mass of water:
Given: mass of water = 0.500 kg
Step 3: Calculate the molality of the solution:
Molality (m) = moles of solute / mass of solvent (in kg)
Molality = moles of urea / mass of water (in kg)
Step 4: Calculate the boiling point elevation:
Boiling point elevation (ΔTb) = Kb * m
Now, let's calculate step by step.
Step 1: Calculate the number of moles of urea:
Number of moles = 15.0 g / 60.06 g/mol ≈ 0.2498 mol
Step 2: Calculate the mass of water:
mass of water = 0.500 kg
Step 3: Calculate the molality of the solution:
Molality (m) = 0.2498 mol / 0.500 kg ≈ 0.4996 mol/kg
Step 4: Calculate the boiling point elevation:
Boiling point elevation (ΔTb) = 0.512 °C/m * 0.4996 mol/kg
ΔTb ≈ 0.255 °C
Therefore, the boiling point of the solution composed of 15.0 g urea in 0.500 kg of water will be elevated by approximately 0.255 °C.
To find the boiling point of a solution, you will need to use the concept of boiling point elevation. The boiling point of a solution is higher than the boiling point of the pure solvent due to the presence of solute particles.
To calculate the boiling point elevation, you can use the following formula:
ΔTb = Kb * m
Where:
ΔTb is the boiling point elevation,
Kb is the molal boiling point elevation constant (specific to the solvent),
m is the molality of the solution.
In this case, urea (NH2)2CO is the solute, and water is the solvent. You need to know the molal boiling point elevation constant (Kb) for water.
For water, the Kb value is approximately 0.512 °C/m.
First, calculate the molality (m) of the urea solution:
Molality (m) = moles of solute / mass of solvent (in kg)
Given that you have 15.0g of urea and 0.500kg (500g) of water, convert the mass of urea to moles using its molar mass:
Molar mass of urea ((NH2)2CO) = (2 * 1.01g) + (4 * 1.008g) + 12.01g + 16.00g = 60.06g/mol
Moles of urea = mass / molar mass = 15.0g / 60.06g/mol
Next, calculate the molality:
m = moles of solute / mass of solvent (in kg)
m = (moles of urea) / (mass of water in kg) = (moles of urea) / 0.500kg
Now, substitute the values into the boiling point elevation formula:
ΔTb = Kb * m
Use the Kb value for water (0.512 °C/m) and the calculated molality to find ΔTb (boiling point elevation).
Finally, add the boiling point elevation to the boiling point of pure water (100°C) to find the boiling point of the solution.