the boiling point of water at 735mmHg is 99.073 degrees celcius. What mass of NaCl should be added to 3.11kg water to increase the boiling point to 100.000 degrees celcius? Kb for water = 0.510 K Kg mol-1
bpelevation= kb*m=kb*mass/58 / 3.11
mass=.827*58*3.11 grams
(you do all that more accurately)
where did the 58 come from?
the equation is bpelevation = kb x m x i. so shouldnt you m= bp elevation/(kb x i)??
To calculate the mass of NaCl needed to increase the boiling point of water, we need to use the formula for boiling point elevation. The formula is:
ΔTb = Kb * m * i
Where:
ΔTb is the change in boiling point
Kb is the molal boiling point elevation constant for water (0.510 K kg mol-1)
m is the molality of the solution in mol/kg
i is the van't Hoff factor, which reflects the number of particles into which the solute separates in the solution
First, let's calculate the change in boiling point (ΔTb):
ΔTb = 100.000 °C - 99.073 °C
ΔTb = 0.927 °C
Since we are adding NaCl to water and NaCl dissociates into two particles (Na+ and Cl-) in solution, the van't Hoff factor (i) for NaCl is 2.
Next, we need to calculate the molality (m) of the solution:
m = moles of solute / mass of solvent (water in this case)
The molar mass of NaCl is 58.44 g/mol. To calculate the moles of NaCl needed, we divide its mass by its molar mass:
moles of NaCl = mass of NaCl / molar mass of NaCl
Now, we can determine the mass of NaCl needed to achieve the desired boiling point elevation.
Let's assume x is the mass of NaCl in grams.
moles of NaCl = x / 58.44 g/mol
molality (m) = moles of NaCl / mass of water (in kg)
molality (m) = (x / 58.44 g/mol) / 3.11 kg
Now we can plug in all the values into the equation ΔTb = Kb * m * i and solve for x:
0.927 °C = (0.51 K kg mol-1) * [(x / 58.44 g/mol) / 3.11 kg] * 2
Simplifying the equation:
0.927 = (0.51 K * 2 * x) / (58.44 g/mol * 3.11 kg)
Solving for x:
x = (0.927 * 58.44 g/mol * 3.11 kg) / (0.51 K * 2)
x ≈ 33.7 g
Therefore, approximately 33.7 grams of NaCl should be added to 3.11 kg of water to increase the boiling point to 100.000 degrees Celsius.