Phosphorous pentachloride decomposes according to the reaction PCl5(g)=PCl3(g)+Cl2(g)

A 12.3 g sample of PCl5 is added to a sealed 1.50 L flask and the reaction is allowed to come to equilibrium at a constant temperature. At equilibrium, 31.8% of the PCl5 remains. What is the equilibrium constant, Kc, for the reaction?

Question is asking for Kc

The equilibrium constant, , for the reaction is 0.061.

Explanation:

Initial concentration of  =  

Equilibrium concentration of =  

The given balanced equilibrium reaction is,

Initial conc.              0.039 M                0 M        0 M

At eqm. conc.     (0.039-x) M              (x) M   (x) M

Given : (0.039-x) = 0.012

x = 0.027

The expression for equilibrium constant for this reaction will be,

Now put all the given values in this expression, we get :

The equilibrium constant, , for the reaction is 0.061.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.