Partial Pressure Problem: Calculating Remaining Reactant using Avogadro's Law

In summary, the gas phase decomposition of ethylamine at 500°C produces ethane and ammonia according to the equation C2H5NH2 (g) → C2H4 (g) + NH3 (g). The partial pressure of the reactant remaining at time t can be found using Avogadro's law and stoichiometry, given an initial pressure of 55 mm Hg and the following total pressures at different times: 0 minutes - 55 mm Hg, 2 minutes - 64 mm Hg, 4 minutes - 72 mm Hg, 10 minutes - 89 mm Hg, 12 minutes - 93 mm Hg. Using these values, the partial pressure of
  • #1
elliotyang
5
0
The gas phase decomposition of ethylamine produces ethane and ammonia according to the following equation:-

C2H5NH2 (g) → C2H4 (g) + NH3 (g)

The following total pressures were found for this reaction at 500°C with an initial pressure of pure ethylamine equal to 55 mm Hg.

Ptotal (mm Hg) time (min)
55 0

64 2

72 4

89 10

93 12


If P0 is the initial pressure of reactant and ptotal is the total pressure at time t, show how the the partial pressure of reactant remaining at time t can be found.

Can anyone give hint to me how to start to solve this question?

is it i have to apply avogadro's law?
 
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  • #2
elliotyang said:
is it i have to apply avogadro's law?

That, plus stoichiometry.
 
  • #3


To solve this problem, you can use Avogadro's law which states that at a constant temperature and pressure, equal volumes of gases contain equal numbers of molecules. This means that the ratio of the number of moles of a gas to its volume is constant. In this case, we can use this law to calculate the number of moles of ethylamine at different times during the reaction.

First, we can use the ideal gas law to calculate the number of moles of ethylamine at the initial time (t=0). The ideal gas law is given by PV=nRT, where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature. In this case, we can rearrange the equation to solve for n and get n=P0V/RT. Since we know the initial pressure (P0) and the temperature (500°C), we can use the given volume to calculate the initial number of moles of ethylamine.

Next, we can use the same equation to calculate the number of moles of ethylamine at different times (t) during the reaction. We know the total pressure (Ptotal) and the temperature (500°C) at each time, and we can use the given volume to calculate the number of moles of the products (C2H4 and NH3). Therefore, we can subtract the number of moles of the products from the initial number of moles of ethylamine to get the number of moles of ethylamine remaining at each time.

Finally, we can use the ideal gas law again to calculate the partial pressure of ethylamine at each time. The partial pressure of a gas is the pressure it would exert if it occupied the same volume alone at the same temperature. Therefore, we can use the calculated number of moles of ethylamine and the given volume to calculate the partial pressure at each time.

In summary, to find the partial pressure of ethylamine remaining at a certain time during the reaction, you can use Avogadro's law to calculate the number of moles of ethylamine at that time, and then use the ideal gas law to calculate the partial pressure.
 

1. What is partial pressure?

Partial pressure is the pressure exerted by an individual gas in a mixture of gases. It is proportional to the number of moles of that gas present in the mixture.

2. How do you calculate partial pressure?

To calculate partial pressure, you multiply the total pressure of the gas mixture by the mole fraction of the gas in question.

3. Why is partial pressure important?

Partial pressure is important because it helps determine the behavior of gases in a mixture. It is used in various gas laws and can also be used to calculate the concentration of a gas in a mixture.

4. What is the relationship between partial pressure and mole fraction?

The relationship between partial pressure and mole fraction is directly proportional. As the mole fraction of a gas increases, so does its partial pressure.

5. How does altitude affect partial pressure?

As altitude increases, the partial pressure of gases decreases. This is because the atmospheric pressure decreases with altitude, resulting in a decrease in the total pressure of gases in the atmosphere.

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