Consider the following system at equilibrium where Delta H degree = -87.9 kJ, an
ID: 487392 • Letter: C
Question
Consider the following system at equilibrium where Delta H degree = -87.9 kJ, and K_c = 83.3, at 500 K. PCI_3(g) + Cl_2(g) PCI_5(g) If the VOLUME of the equilibrium system is suddenly increased at constant temperature: The value of K_c increases. decreases. remains the same. The value of Qc is greater than K_c is equal to K_c. is less than K_c. The reaction must run in the forward direction to re-establish equilibrium. run in the reverse direction to reestablish equilibrium. remain the same. It is already at equilibrium. The number of moles of cl_2 will: increase. decrease. remain the same.Explanation / Answer
part a
The value of Kc varies with only temperature. As the T is same, the Kc value also remains same
Part B
we can write the Kc = {moles(PCl5)/V} /{ moles of PC3/V x moles of Cl2/V}
= moles PCl5 x V /moles of PCl3 x moles of Cl2
Thus to maintain Kc same with increase in volume , moles of PCl5 decrease.
Thus Qc which has same expression as Kc , becomes less than Kc
Thus Qc< Kc
part C
As Qc < Kc, the reaction goe sin forward direction.
Part C moles of Cl2 further decrease as the reaction goes forward/ rate of forward reaction increases.