Partial Pressures Problem

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In summary, at 50% completion of the reaction where 9.0g of glucose remains, the partial pressures of CO2 and O2 are both 370 torr and the partial pressure of H2O is 42 torr at a temperature of 35 degrees C and pressure of 780 torr.
  • #1
grapejellypie
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C6H12O6 (glucose) +6O2 ---> 6CO2 + 6H2O

If this reaction is carried out in an expandable container at 35degrees C and 780 torr, what is the partial pressure of each gas when the reaction is 50% complete (9.0 g of glucose remains)?



I know that 35 degrees C = 308.15k and that 780 torr = 1.03 atm. I also know that at 35degrees C, the vapor pressure of water is always 42.2 torr (0.056 atm).
If 9.0g of glucose remain, then there are 0.05 mol of glucose, 0.3 mol of CO2, 0.3 mol of O2, and 0.3 mol of H2O

I subtracted 0.056 atm from 1.03 atm to get .974 atm and used the equatoin Partial Pressure of X = (Molar Ratio of X) x Total Pressure. (Molar Ratio = Mol X/ Total Mols in Sample). However, this did not produce the answer in the back of the book, which reads that the partial pressures of CO2 and H2O are both 3.7 x 10^2 torr.
 
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  • #2
Most likely what they mean is that CO2 and O2 have both partial pressures of 370 torr. 370 torr CO2 + 370 torr O2 + 42 H2O gives around 780, which fits.
 
  • #3


I would first verify the accuracy of the information and calculations provided in the question. It is important to double check the given values for temperature and pressure and make sure that the correct units are being used. Additionally, the molar ratio of each gas should be calculated based on the balanced chemical equation to ensure accuracy.

Assuming that the given values are correct, I would approach this problem by first converting the temperature to Kelvin (308.15K) and the pressure to atmospheres (1.03 atm). Then, using the ideal gas law (PV = nRT), I would calculate the total number of moles present in the system at 50% completion (0.35 mol). From this, I would determine the molar ratio of each gas (CO2, O2, and H2O) based on the balanced chemical equation (6:6:6).

Next, I would use the partial pressure equation (Partial Pressure of X = (Molar Ratio of X) x Total Pressure) to calculate the partial pressure of each gas. This should result in a partial pressure of 3.7 x 10^2 torr for both CO2 and H2O, as given in the answer key. If this does not match the provided answer, I would double check my calculations and make sure all units are consistent.

In conclusion, as a scientist, it is important to carefully analyze and verify the information provided and use accurate calculations to determine the partial pressures of each gas in a given system.
 

1. What is a partial pressure problem?

A partial pressure problem is a type of calculation in chemistry that involves determining the partial pressure of a gas in a mixture. This is typically done using the ideal gas law, which relates the pressure, volume, and temperature of a gas.

2. How do you calculate partial pressure?

To calculate the partial pressure of a gas in a mixture, you can use the formula P = X * Ptotal, where P is the partial pressure, X is the mole fraction of the gas, and Ptotal is the total pressure of the mixture. Alternatively, you can use the ideal gas law (PV = nRT) to solve for the partial pressure.

3. What is the significance of partial pressure?

Partial pressure is important because it helps us understand the behavior of gases in mixtures. It can also be used to determine the concentration of a gas in a mixture, as well as predict how gases will react with each other.

4. How does temperature affect partial pressure?

According to the ideal gas law, as temperature increases, the pressure of a gas will also increase, assuming the volume and moles of the gas remain constant. This means that as temperature increases, the partial pressure of a gas in a mixture will also increase.

5. What are some real-world applications of partial pressure problems?

Partial pressure problems are commonly used in industries such as chemical manufacturing, where precise control of gas mixtures is necessary. They are also important in fields like environmental science, where understanding the partial pressures of gases in the atmosphere can help predict and mitigate the effects of air pollution.

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