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My question is on the answer explanation. i have provided the question and the chemical reaction for reference. For the answer explanation (i have colored in pink the confusing part), how do we estimate the magnitude of x and how do we know that more than half units need to shift over?? Why is it more than half and not more than a quarter, what is the relation between this and Keq? Thank you.
PCl3(g) + Cl2(g) <---> PCl5(g)
17. If a flask were filled with PCI3 and CI2 to a total
pressure of 1.50 atm. such that the mole fraction of PCI3 is twice that of CI2, then what is the total pressure of the system once at equilibrium?
A . Less than 1.00 atm.
B . Between 1.00 atm. and 1.25 atm.
C . Between 1.25 atm. and 1.50 atm.
D . Greater than 1.50 atm.
Answer: B, To solve this question, use the formula X Pj = Ptotal- ln this case the following holds true:
Ptotal = PPCI3 + PC12 + pPCl5 = (1 " x) + (0-5 - x) + x = 1.5 - x.
If everything reacted to the limiting reagent capacity, then x is 0.5. But the reaction does not go to completion, so the value of x falls between 0 and 0.5. To solve this question, you must estimate the magnitude of x. The value of x is greater than 0.25, because over half shifts to products to reach an equilibrium constant of 1.95. This makes choice B the best answer.
PCl3(g) + Cl2(g) <---> PCl5(g)
17. If a flask were filled with PCI3 and CI2 to a total
pressure of 1.50 atm. such that the mole fraction of PCI3 is twice that of CI2, then what is the total pressure of the system once at equilibrium?
A . Less than 1.00 atm.
B . Between 1.00 atm. and 1.25 atm.
C . Between 1.25 atm. and 1.50 atm.
D . Greater than 1.50 atm.
Answer: B, To solve this question, use the formula X Pj = Ptotal- ln this case the following holds true:
Ptotal = PPCI3 + PC12 + pPCl5 = (1 " x) + (0-5 - x) + x = 1.5 - x.
If everything reacted to the limiting reagent capacity, then x is 0.5. But the reaction does not go to completion, so the value of x falls between 0 and 0.5. To solve this question, you must estimate the magnitude of x. The value of x is greater than 0.25, because over half shifts to products to reach an equilibrium constant of 1.95. This makes choice B the best answer.