Molality creating problems for me

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In summary, the conversation discusses the calculation of molality and osmotic pressure for a 0.5% solution of urea in water at 0 degrees celsius. The osmotic pressure is successfully calculated as 1.86 atm, but the issue at hand is determining the molality due to the lack of information on the mass of the solute.
  • #1
shaiqbashir
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Molality creating problems for me!

calculate the molality and osmotica pressur of a 0.5% solution of urea (Mol Mass=60) in water at 0 degree celsius.

R-0.0821

now my dear friends!

i have calculated successfuly the osmotic pressure in this question which is

osmotic pressure = 1.86 atm

now the problem is this that how to calculate this molality. i know that

molality = no of moles of the solute/ mass of the solvent in kilograms

but you see that here i don't have any masss of the solute given at all.

Please help me

Thanks in advance
 
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  • #2
Such diluted solution has density almost identical with the density of pure water.
 
  • #3


Dear colleague,

I understand that molality can be a tricky concept to grasp, but it is an important one in chemistry and can help us understand solutions better. In this case, we are dealing with a 0.5% solution of urea in water at 0 degrees Celsius. To calculate the molality, we need to first determine the number of moles of solute present in the solution. We can do this by using the formula:

moles of solute = mass of solute (in grams) / molar mass of solute

In this case, the mass of solute is not given, but we can calculate it using the concentration of the solution (0.5%) and the volume of the solution. Since we are dealing with a 0.5% solution, it means that there is 0.5 grams of urea in 100 mL of solution. This can be converted to 5 grams of urea in 1000 mL (1 L) of solution.

Now, using the molar mass of urea (60 g/mol), we can calculate the number of moles of urea present in the solution:

moles of urea = 5 g / 60 g/mol = 0.0833 mol

Next, we need to calculate the mass of the solvent (water) in kilograms. Since we have 1000 mL of solution, it means we have 1000 mL of water. We can convert this to kilograms by dividing by 1000:

mass of water = 1000 mL / 1000 = 1 kg

Now, we can use these values to calculate the molality:

molality = 0.0833 mol / 1 kg = 0.0833 m

I hope this helps you understand how to calculate molality in this situation. If you have any further questions, don't hesitate to ask. Good luck with your studies!
 

What is molality and why does it create problems for me?

Molality is a measure of the concentration of a solution expressed in moles of solute per kilogram of solvent. It can create problems for scientists because it is not affected by changes in temperature, making it a more accurate measure of concentration for reactions involving temperature changes.

How do I calculate molality?

Molality is calculated by dividing the moles of solute by the mass of the solvent in kilograms. The formula for molality is molality (m) = moles of solute (n) / mass of solvent in kilograms (kg).

Why is molality preferred over molarity in some cases?

Molality is preferred over molarity in reactions involving temperature changes because it is not affected by temperature. Molarity, on the other hand, is affected by changes in temperature, making it a less accurate measure of concentration in these types of reactions.

What are some common problems encountered when using molality?

One common problem with molality is that it can be difficult to measure the mass of the solvent accurately, leading to errors in the calculation. Another issue is that molality is not as commonly used as molarity, so it may be unfamiliar to some scientists.

How can I overcome problems with molality?

To overcome problems with molality, it is important to accurately measure the mass of the solvent and ensure that it is expressed in kilograms. Additionally, practicing and becoming familiar with the concept of molality can help overcome any difficulties in using this measure of concentration.

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