In many thruster systems used for spacecraft attitude control, hydrazine (N2H4) is used as the propellant. The hydrazine is stored as a liquid, but before reaching the nozzle, it passes through a heated catalyst bed. In the bed, not only does the hydrazine vaporize, but it also exothermically decomposes (thereby raising the temperature) into ammonia (NH3) and hydrogen (H2). However, some of the ammonia also decomposes (endothermically) into H2 and N2. Consider a hydrazine thruster where the conditions of the gases exiting the catalyst bed are 1300 K and 22 bar. The table below gives the formation enthalpies and equilibrium constant for the formation reaction of each of the listed species at the noted temperatures.
a) Determine the composition (mole fractions) of the products exiting the catalyst bed assuming: 1) the hydrazine has been completely consumed and the only product species are N2, H2, and NH3; and 2) the gas is in chemical equilibrium.
b) Would changing the pressure from 22 bar to 12 bar increase the mole fraction of NH3 leaving the catalyst bed (assume no change in the exit temperature)? You do not need to calculate a specific number, but a yes/no answer by itself is not sufficient; you need to justify your answer.
c) ESTIMATE the mole fraction of H in the products exiting the catalyst chamber. For this estimate, you can assume that all your calculations above (which did not include the presence of H) are
In many thruster systems used for spacecraft attitude control, hydrazine (N2H4) is used as the propellant. The hydrazine is stored as a liquid, but before reaching the nozzle, it passes through a heated catalyst bed. In the bed, not only does the hydrazine vaporize, but it also exothermically decomposes (thereby raising the temperature) into ammonia (NH3) and hydrogen (H2). However, some of the ammonia also decomposes (endothermically) into H2 and N2. Consider a hydrazine thruster where the conditions of the gases exiting the catalyst bed are 1300 K and 22 bar. The table below gives the formation enthalpies and equilibrium constant for the formation reaction of each of the listed species at the noted temperatures.
a) Determine the composition (mole fractions) of the products exiting the catalyst bed assuming: 1) the hydrazine has been completely consumed and the only product species are N2, H2, and NH3; and 2) the gas is in chemical equilibrium.
b) Would changing the pressure from 22 bar to 12 bar increase the mole fraction of NH3 leaving the catalyst bed (assume no change in the exit temperature)? You do not need to calculate a specific number, but a yes/no answer by itself is not sufficient; you need to justify your answer.
c) ESTIMATE the mole fraction of H in the products exiting the catalyst chamber. For this estimate, you can assume that all your calculations above (which did not include the presence of H) are
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