A 4.47 g sample of a molecular compound is dissolved in 96 g of tetrachloromethane. The normal boiling point of the solution is 61.51 degrees celcius, the normal boiling point for CCl4 is 61.2 degrees celsius. The boiling point constant for CCl4 is 4.95K*kg/mol. What is the molar mass of the compound? Answer in units of g/mol
I know you have to use the formula:
delta Tb = iKbm but I have no clue how start or find the molality.
PLEASE HELP
To find the molar mass of the compound, you need to determine the molality (m) of the solution first.
To find the molality, you can use the formula:
m = (moles solute) / (mass solvent in kg)
Step 1: Convert the mass of the compound from grams to moles.
Given:
Mass of compound (solute) = 4.47 g
To convert to moles, you need the molar mass of the compound. Let's assume the molar mass is M.
Moles of compound = Mass of compound / M
Step 2: Convert the mass of the solvent to kg.
Given:
Mass of solvent (CCl4) = 96 g
Mass of solvent in kg = Mass of solvent (g) / 1000
Step 3: Calculate the molality.
m = (moles of compound) / (mass of solvent in kg)
Now that you have the molality (m), you can use the given boiling point constant (Kb) and the change in boiling point (∆Tb) to find the moles of solute in the solution.
∆Tb = i * Kb * m
From the information given, the change in boiling point (∆Tb) is the difference between the boiling point of the solution and the boiling point of pure CCl4.
∆Tb = 61.51 °C - 61.2 °C = 0.31 °C
i is the van't Hoff factor, which represents the number of particles formed when the solute is dissolved. Assuming the compound is non-electrolytic, i would be 1.
Now you can rearrange the equation to solve for moles of solute:
moles of solute = (∆Tb) / (i * Kb * m)
Finally, you can find the molar mass (M) of the compound by rearranging the equation:
Molar mass (M) = (mass of compound) / (moles of solute)
Substituting the calculated values into the equation will give you the answer in units of g/mol.
I hope this helps! Let me know if you have any further questions.
To find the molar mass of the compound, you need to determine the change in boiling point (ΔTb) of the solution and the molality (m) of the solution. Let's break down the steps:
Step 1: Calculate ΔTb (change in boiling point):
ΔTb = Normal boiling point of the solution - Normal boiling point of the solvent
= 61.51°C - 61.2°C
= 0.31°C
Step 2: Calculate molality (m):
Molality refers to the number of moles of solute dissolved in one kilogram of solvent. To find the molality, you need to know the number of moles of the solute and the mass of the solvent.
First, convert the mass of the solute from grams to moles:
Number of moles of the solute = mass of the solute (g) / molar mass of the solute (g/mol)
To find the number of moles of the solute, you need the mass of the solute. In this case, the mass of the solute is given as 4.47 g.
Now, you need to find the number of moles of the solvent:
Number of moles of the solvent = mass of the solvent (g) / molar mass of the solvent (g/mol)
To find the number of moles of CCl4 (tetrachloromethane), you need the mass of CCl4. In this case, the mass of CCl4 is given as 96 g.
Step 3: Calculate molality (m):
Molality (m) = moles of solute / kilograms of solvent
= (moles of solute) / (mass of solvent in kg)
You have the number of moles of solute and solvent from the previous steps, and you need to convert the mass of the solvent from grams to kilograms:
Mass of solvent (kg) = mass of solvent (g) / 1000
Step 4: Calculate the molar mass of the compound:
Now that you have ΔTb and molality, you can rearrange the equation ΔTb = iKbm to solve for the molar mass (M) of the compound:
Molar mass (g/mol) = (ΔTb / (iKb)) / molality
In this case, the boiling point constant (Kb) for CCl4 is given as 4.95 K*kg/mol, and since this is a molecular compound, the "i" value is 1 (since it does not dissociate into ions).
Plug in the values for ΔTb, i, Kb, and molality into the equation to find the molar mass of the compound.
I hope this explanation helps you understand how to approach and solve the problem.
Note the correct spelling of celsius.
Why don't you start with delta T = i*Kb*m
You can calculate delta T, i = 1 since it is a molecular compound, you know Kb and solve for m.
Then m = mols/kg solvent. You know m and kg solvent, solve for mols.
Then mols = grams/molar mass. You know mols and grams, solve for molar mass.