Organic Compound's Mass from Vapor Pressure

In summary, the boiling temperature of a natural product (MW = 150 g/mol) with steam at atmospheric pressure is 99 C, with the vapor pressure of water at 99 C being 733 mmHg. To calculate the weight of the natural product that codistills with each gram of water at 99 C, the ratio of moles of the natural product to moles of water is used, resulting in a value of 8.64 g of natural product per gram of water. To recover the natural product from 0.5 g of spice with 10% desired substance, 0.00579 g of water must be removed through steam distillation.
  • #1
Soaring Crane
469
0
Is this even correct?


A natural product (MW = 150 g/mol) distills with steam at a boiling temperature of 99 C at atmospheric pressure. The vapor pressure of water at 99 C is 733 mmHg.

a. Calculate the weight of the natural product that codistills with each gram of water at 99 C.


(P*_a)/(P*_b) = moles A / moles B
P*_a = 760 torr
P*_b = 733 torr

ratio 760 moles/733 moles water = 1.0368 mol/1 mol water
1.0368 mol (150 g/mol) = 155.52 g organic compound / (18.0 g water) = 8.64 g/ 1 g water ?



b. How much H2O must be removed by steam distillation to recover this natural product from 0.5 g of spice that contains 10 % of the desired substance?

5 g*(.10) = .05 g desired substance

0.05 g (1 g water/8.64 g organic) = 0.00579 g water

Thanks.
 
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  • #2
A natural product (MW = 150 g/mol) distills with steam at a boiling temperature of 99 C at atmospheric pressure. The vapor pressure of water at 99 C is 733 mmHg.

a. Calculate the weight of the natural product that codistills with each gram of water at 99 C.


(P*_a)/(P*_b) = moles A / moles B
P*_a = 760 torr
P*_b = 733 torr

ratio 760 moles/733 moles water = 1.0368 mol/1 mol water
1.0368 mol (150 g/mol) = 155.52 g organic compound / (18.0 g water) = 8.64 g/ 1 g water ?
No, the amount of the organic compound should be much smaller, with respect to the mole value. Assuming the effects
of boiling point elevation is not important here, you can simply account for the mole ratio of the solute...

(760 mmHg-733 mmHg)/733 mmHg=mole ratio of solute/moles of water

b. How much H2O must be removed by steam distillation to recover this natural product from 0.5 g of spice that contains 10 % of the desired substance?

5 g*(.10) = .05 g desired substance

0.05 g (1 g water/8.64 g organic) = 0.00579 g water

Thanks.

The method here seems appropriate.
 
  • #3


I would say that the calculations provided seem to be correct based on the given information. However, it is always important to double check the calculations and make sure all units are consistent. Additionally, the vapor pressure of water may change at different temperatures and pressures, so it is important to consider those variables as well. Overall, the concept of determining the mass of an organic compound through vapor pressure is a valid and commonly used method in scientific research.
 

Related to Organic Compound's Mass from Vapor Pressure

1. What is the relationship between vapor pressure and mass of organic compounds?

The mass of an organic compound is directly proportional to its vapor pressure. As the mass of the compound increases, so does its vapor pressure. This is because a larger mass will have more molecules present, leading to a higher vapor pressure.

2. How does the molecular structure of an organic compound affect its vapor pressure?

The molecular structure of an organic compound can greatly impact its vapor pressure. Compounds with stronger intermolecular forces, such as hydrogen bonding, will have lower vapor pressure compared to compounds with weaker forces. This is because the stronger forces hold the molecules together, making it harder for them to escape into the gas phase.

3. Can the vapor pressure of an organic compound be used to determine its molecular mass?

Yes, the vapor pressure of an organic compound can be used to calculate its molecular mass. By using the ideal gas law, PV = nRT, where P is vapor pressure, V is volume, n is moles, R is the gas constant, and T is temperature, the molecular mass can be determined by solving for n. This method is known as the vapor density method.

4. How does temperature affect the vapor pressure of organic compounds?

In general, an increase in temperature will cause an increase in vapor pressure of organic compounds. This is because higher temperatures provide more energy for the molecules to overcome intermolecular forces and escape into the gas phase. However, this relationship may not hold true for all compounds, as some may have a decrease in vapor pressure with increasing temperature due to changes in intermolecular forces.

5. What is the significance of measuring the vapor pressure of organic compounds?

Measuring the vapor pressure of organic compounds is important for various reasons. It can provide information about the physical properties of a compound, such as its boiling point and intermolecular forces. It is also helpful in industrial and environmental applications, as it can aid in the design of processes and equipment, and in predicting the behavior of pollutants in the atmosphere.

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