Problem: For the reaction system      H2(g) + X2(g) ⇌ 2 HX(g)Kc = 24.4 at 300 K. If the reaction is set up with the following initial concentrations, what will the equilibrium concentration of X2 be? initial H2 = 0.150 M          initial X2 = 0.200 M          initial HX = 0.600 MA. 0.0365 M B. 0.114 M C. 0.164 M D. 0.0730 ME. 0.500 M

We are being asked to calculate the equilibrium concentration of X₂ for the given equilibrium reaction:

   H₂(g) + X₂(g) ⇌ 2 HX(g)            K_c = 24.4 at 300 K. 

When dealing with equilibrium and K_c:

• K_c → equilibrium units are in molarity 
• K_c is an equilibrium expression:

$\boxed{{\mathbf{K}}_{\mathbf{c}}\mathbf{=}\frac{\mathbf{products}}{\mathbf{reactants}}}$

▪ only aqueous and gaseous species are included in the equilibrium expression
▪ the coefficient of each compound in the reaction equation will be the exponent of the concentrations in the equilibrium expression

Given:    

Initial Concentrations:

initial H₂ = 0.150 M          

initial X₂ = 0.200 M         

initial HX = 0.600 M

Let’s calculate the Reaction Quotient (Q) using the given initial concentration to determine which direction the equilibrium will proceed:

$\boxed{\mathbf{Q}\mathbf{=}\frac{\mathbf{products}}{\mathbf{reactants}}}$