Question

0.074 mol PCI5 (g) are placed in a 1l tube. After the equilibrium PCI5(g)= PCI3 + Cl2 has been reached at a certain temperature, PCI3= 0.05 mol/l. What are the equilibrium concentrations of PCI3and Cl₂ and what is the K.?​

Answer 1

The equilibrium concentrations of PCl3 and Cl2 are both 0.05 M, and the equilibrium concentration of PCl5 is 0.024 M. The equilibrium constant (K) for the reaction is approximately 0.1042.

Step-by-step explanation:

To determine the equilibrium concentrations of PCl3 and Cl2 along with the equilibrium constant (K), we can use the information provided about the initial moles of PCl5 and the equilibrium concentration of PCl3. Since PCl5 decomposes into PCl3 and Cl2 in a 1:1:1 ratio, we know that if PCl3 is 0.05 mol/L at equilibrium, Cl2 would also be 0.05 mol/L because for every mole of PCl3 produced, one mole of Cl2 is also produced. Knowing the initial moles of PCl5 (0.074 mol) and the volume of the container (1L), the initial concentration of PCl5 is 0.074 M. At equilibrium, some of the PCl5 has decomposed so we subtract the moles of PCl3 formed (also the amount of Cl2 formed) from the initial moles of PCl5 to find the equilibrium concentration of PCl5, which would be 0.074 M - 0.05 M = 0.024 M.

The equilibrium constant (K) can then be calculated using the relationship K = [PCl3][Cl2]/[PCl5]. Plugging in the equilibrium concentrations, we get K = (0.05)(0.05)/(0.024), which is approximately 0.1042.