Cocaine is a non-electrolyte that has a molecular weight of 303.4 g/mole. How many grams must be dissolved in 25.0 mL of Chloroform (density = 1.484 g/mL) to raise its boiling point to 65.5 Celsius? The boiling point of pure Chloroform is 61.2 Celsius.

Question

Cocaine is a non-electrolyte that has a molecular weight of 303.4 g/mole. How many grams must be dissolved in 25.0 mL of Chloroform (density = 1.484 g/mL) to raise its boiling point to 65.5 Celsius? The boiling point of pure Chloroform is 61.2 Celsius.

Kb Chloroform = 3.62 Celsius/m

Answer 1

Calculate delta T for CH3Cl3.

delta T = Kb*m
Solve for m

m = moles/kg solvent
Solve for moles.

moles cocaine = grams/molar mass
Solve for grams.

Answer 2

To solve this problem, we can use the formula for boiling point elevation:

ΔT = Kb * m

where ΔT is the change in boiling point, Kb is the molal boiling point elevation constant of the solvent, and m is the molality of the solute.

First, let's calculate the change in boiling point (ΔT):

ΔT = boiling point of the solution - boiling point of the pure solvent
ΔT = 65.5 °C - 61.2 °C
ΔT = 4.3 °C

Next, we need to calculate the molality of the solute (m). We can find the mass of the solute using the density and volume provided.

Mass of Chloroform = Volume * Density
Mass of Chloroform = 25.0 mL * 1.484 g/mL
Mass of Chloroform = 37.1 g

Since cocaine is a non-electrolyte, it doesn't dissociate in the solvent. Therefore, the molar mass of cocaine is equal to its molecular weight.

Now we can calculate the molality (m) using the following formula:

m = (moles of solute) / (mass of solvent in kg)

First, let's calculate the moles of Cocaine:

moles of Cocaine = mass of Cocaine / molar mass of Cocaine
moles of Cocaine = 303.4 g / mol

Next, let's convert the mass of the solvent to kg:

mass of Chloroform (kg) = mass of Chloroform (g) / 1000
mass of Chloroform (kg) = 37.1 g / 1000
mass of Chloroform (kg) = 0.0371 kg

Now we can calculate the molality:

m = (moles of Cocaine) / (mass of Chloroform in kg)
m = (303.4 g / mol) / (0.0371 kg)
m = 8200 mol/kg

Finally, let's plug in the values into the boiling point elevation formula:

ΔT = Kb * m
4.3 °C = (3.62 °C/mol) * (8200 mol/kg)

To find the mass of Cocaine, we can isolate it in the formula:

Mass of Cocaine = (ΔT * mass of solvent in kg) / (Kb * m)

Mass of Cocaine = (4.3 °C * 0.0371 kg) / (3.62 °C/mol * 8200 mol/kg)
Mass of Cocaine = 0.037 * 0.0371 / (3.62 * 8200)
Mass of Cocaine = 0.00136738 / 29764 = 4.59 * 10^(-8) g

Therefore, approximately 4.59 * 10^(-8) grams of Cocaine must be dissolved in 25.0 mL of Chloroform to raise its boiling point to 65.5 °C.