A 200.0g sample of glucose(180.16g/mol, Kmp=1.86 degrees celcius/m, mp=146 degrees celcius)is contaminated with 5.000g of table salt, sodium chloride(58.44g/mol, mp=801 degrees celcius). What would the expected melting point of the mixture be?
I assume NaCl does not ionize when dissolved in glucose.
mols NaCl = grams/molar mass.
Subsittute and solv for mols NaCl.
Then m = molality NaCl = mols/kg solvent
Substitute mols from above and kg solvent is 0.200 kg, and solve for m.
Then delta T = Kf*m
You have Kf for glucose in the problem and you've solved for m, calculate delta T.
Finally, subtract delta T from the normal melting point of glucose.
Thanks, DrBob222
is the answer 141.67 pleaase help?
МХГЖ
To determine the expected melting point of the mixture, we need to use the concept of colligative properties, specifically the phenomenon known as "freezing point depression."
Colligative properties are properties that depend on the number of particles dissolved in a solution, rather than the particular type of particles. Freezing point depression is one such colligative property, which states that the freezing point of a solution is lower than the freezing point of the pure solvent.
The formula for calculating the freezing point depression is:
ΔTf = Kf * m
Where:
ΔTf = freezing point depression
Kf = molal freezing point depression constant (specific for each solvent)
m = molality of the solution (moles of solute per kilogram of solvent)
First, we need to calculate the molality (m) of the glucose solution. We can use the following formula:
m = (moles of solute) / (mass of solvent in kg)
Given:
Mass of glucose (solute) = 200.0 g
Molar mass of glucose = 180.16 g/mol
moles of solute = (mass of solute) / (molar mass of solute)
= 200.0 g / 180.16 g/mol
Next, we need to calculate the molality (m) using the mass of the solvent.
mass of solvent = mass of glucose - mass of salt
= 200.0 g - 5.000 g
Now, we need the molal freezing point depression constant (Kf) for glucose.
From the information you provided, the value is 1.86 degrees Celsius/m.
Now, we can calculate the freezing point depression (ΔTf):
ΔTf = Kf * m
Finally, we can calculate the expected melting point of the mixture by subtracting the freezing point depression from the freezing point of the pure solvent.
Expected melting point = (melting point of pure solvent) - (ΔTf)
Given:
Melting point of glucose = 146 °C
Using the above formulas and given information, we can calculate the expected melting point of the mixture.