Q16 of 73 Page 224

What is the equilibrium concentration of each of the substances in the equilibrium when the initial concentration of ICl was 0.78 M?

2ICl (g) ⇌ I2 (g) + Cl2 (g); Kc= 0.14

For the given reaction, let’s assume that the molar concentration of I2 and Cl2 at equilibrium is x mol/L.

The given reaction is


2ICl (g) ⇌ I2 (g) + Cl2 (g)


Initial concentration 0.78M 0 0


Equilibrium concentration (0.78-2x)M x x


Equilibrium constant (Kc) is defined as a number that expresses the relationship between the amounts of products and reactants present at equilibrium in a reversible chemical reaction at a given temperature.


Here, Kc = 0.14


For the given reaction,



Where, [I2]=concentration of I2 in mol/L at equilibrium


[Cl2]=concentration of Cl2 in mol/L at equilibrium


[ICl]=concentration of ICl in mol/L at equilibrium





X = 1.67


Therefore, at equilibrium,


[H2]=[I2]=0.167 M


[ICl]= 0.78 - (2x0.167) = 0.446 M


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(i) Write the concentration ratio (reaction quotient), Qc, for this reaction (note: water is not in excess and is not a solvent in this reaction)


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