Calculating Molal Boiling point elevation constant HELP

In summary, the conversation discusses calculating the molal boiling point elevation constant for carbon disulfide (CS2) using information such as its boiling point, density, and the amount of solute dissolved in a given volume of CS2. The formula used is ΔT_{b}=k_{b}(molality), and after solving for the molality and using the given values, the molal boiling point elevation constant is found to be 1.856. The conversation also touches on finding the mass of CS2 by using the given volume and density.
  • #1
piggyxchu
7
0
Calculating Molal Boiling point elevation constant! HELP!

So here's how I did my problem, but the answer I arrived with is wrong. I need help with this...:cry:

Carbon disulfide (CS2) boils at 46.30°C and has a density of 1.261g/mL.
When 0.250 mol of a nondissociating solute is dissolved in 400.0 mL of CS2, the solution boils at 47.46°C. What is the molal boiling point elevation constant for CS2?

Homework Statement


Normal Boiling Point: 46.3°C
0.250mol of solute
400.0mL of CS2 (solvent)

Homework Equations


ΔT[itex]_{b}[/itex]=k[itex]_{b}[/itex](molality)

The Attempt at a Solution


ΔT[itex]_{b}[/itex]=47.46-46.30=1.16°C
molality = 0.250mol/0.400kg = 0.625m

k[itex]_{b}[/itex]= ΔT[itex]_{b}[/itex]/molality.
k[itex]_{b}[/itex]=1.16°C/0.625=1.856.
 
Last edited:
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  • #2


piggyxchu said:
0.400kg

Try harder.
 
  • #3


Borek said:
Try harder.
lol word

piggy, you are given the volume and the density. you want to find the mass, so what do you do?
 

1. What is the molal boiling point elevation constant?

The molal boiling point elevation constant, also known as the ebullioscopic constant, is a physical constant that relates the change in boiling point of a solvent to the molality (moles of solute per kilogram of solvent) of a solution.

2. How do you calculate the molal boiling point elevation constant?

The molal boiling point elevation constant can be calculated by dividing the change in boiling point (in degrees Celsius) by the molality of the solution and the boiling point elevation constant of the solvent. This can be represented by the equation ΔTb = Kbm, where ΔTb is the change in boiling point, Kb is the boiling point elevation constant, and m is the molality of the solution.

3. What is the significance of the molal boiling point elevation constant?

The molal boiling point elevation constant is an important tool in understanding the behavior of solutions and their boiling points. It is used in various industries such as chemistry, biochemistry, and food science to determine the concentration of a solution and other properties such as osmotic pressure and freezing point depression.

4. How does the molal boiling point elevation constant vary for different solvents?

The molal boiling point elevation constant varies for different solvents because it is dependent on the properties of the solvent, such as its molecular weight and boiling point. For example, the molal boiling point elevation constant for water is 0.512 °C/m, while for benzene it is 2.53 °C/m.

5. What factors can affect the accuracy of calculating the molal boiling point elevation constant?

The accuracy of calculating the molal boiling point elevation constant can be affected by various factors such as experimental errors, variations in the properties of the solvent, and the presence of impurities in the solution. It is important to carefully measure and control these variables in order to obtain accurate results.

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