Final answer:
To find the mass of hexachlorophene to be added to chloroform, we can use the formula for boiling point elevation and calculate the molality of the solution. Substituting the given values, the mass of hexachlorophene is found to be 19.6 g.
Step-by-step explanation:
To find the mass of hexachlorophene to be added to chloroform, we need to use the formula for boiling point elevation:
ΔT = K_b*m
Where ΔT is the change in boiling point, K_b is the molal boiling point elevation constant (in °C/m), and m is the molality of the solution.
First, let's calculate the change in boiling point:
ΔT = boiling point of solution - boiling point of pure solvent
ΔT = 62.6°C - 61.2°C
ΔT = 1.4°C
Next, we need to calculate the molality of the solution:
m = moles of solute / mass of solvent in kg
Substituting the given values:
m = (mass of hexachlorophene / molar mass of hexachlorophene) / (mass of chloroform / 1000)
We can rearrange this equation to solve for the mass of hexachlorophene:
mass of hexachlorophene = molar mass of hexachlorophene * (mass of chloroform / 1000) * m
Substituting the given values:
mass of hexachlorophene = 406.9 g/mol * (125 g / 1000) * (1.4°C / (3.63°C/m))
mass of hexachlorophene = 19.6 g
Therefore, the mass of hexachlorophene that must be added to 125 g of chloroform is 19.6 g. Answer choice A is correct.