Gaseous phosphorus pentachloride decomposes to gaseous phosphorus trichloride and chlorine at a temperature where K= 1.0x10^-3 mol/L. Suppose 2.0 mole of phosphorus pentachloride in a 2.0-L vessel is allowed to come to equilibrium. Calculate the equilibrium concentrations of all species.

[PCl₃] = 0.031M

[Cl₂] = 0.031M

[PCl₅] = 0.969M

Explanation:

Based on the reaction:

PCl₅(g) ⇄ PCl₃(g) + Cl₂(g)

Keq is defined as:

Keq = 1.0x10⁻³ = [PCl₃] [Cl₂] / [PCl₅]

Where [] are equilibrium concentrations of each species

Inital [PCl₅] = 2.0mol / 2.0L = 1M.

In equilibrium:

[PCl₃] = X

[Cl₂] = X

[PCl₅] = 1M-X

Where X is reaction coordinate

Solving for X in Keq:

1.0x10⁻³ = [X] [X] / [1-X]

1.0x10⁻³ - 1.0x10⁻³X = X²

1.0x10⁻³ - 1.0x10⁻³X - X² = 0

X:

X = -0.032M. False solution, there is no negative concentration

X = 0.031M

That means equlibrium concentrations are:

[PCl₃] = 0.031M

[Cl₂] = 0.031M

[PCl₅] = 1-0.031M = 0.969M

solute : a solute is a substance that is dissolved in another substance is known as a solvent. it is mixed with a special mixture know as homogeneous mixture.

solvent: a solvent is a substance that dissolved a solute, which results in a solution is known as solvent.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.