At high temperature, 2.00 mol of HBr was placed in a 4.00 L container where it decomposed in the reaction: 2HBr(g) H2(g) Br2(g) At equilibrium the concentration of Br2 was measured to be 0.0955 M. What is Kc for this reaction at this temperature

Respuesta :

Answer: [tex]K_c[/tex] for this reaction at this temperature is 0.029

Explanation:

Moles of  [tex]HBr[/tex] = 2.00 mole

Volume of solution = 4.00 L

Initial concentration of [tex]HBr=\frac{moles}{Volume}=\frac{2.00}{4.00L}=0.500M[/tex]

The given balanced equilibrium reaction is,

                            [tex]2HBr(g)\rightleftharpoons H_2(g)+Br_2(g)[/tex]

Initial conc.              0.500 M              0  M        0 M  

At eqm. conc.            (0.500-2x) M   (x) M   (x) M

The expression for equilibrium constant for this reaction will be,

[tex]K_c=\frac{[H_2\times [Br_2]}{[HBr]^2}[/tex]

Equilibrium concentration of [tex][Br_2][/tex] = x =  0.0955 M

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

[tex]K_c=\frac{0.0955\times 0.0955}{0.500-2\times 0.0955}[/tex]

[tex]K_c=0.029[/tex]

Thus [tex]K_c[/tex] for this reaction at this temperature is 0.029

The Kc for this reaction at this temperature is 0.0955.

Calculation of the Kc:

Since

Initial moles of HBr,n = 2.00 mol

The volume of the container, V = 4.00 L

So,

initial concentration of HBr

= n/V = 2.00mol/4.00L

= 0.50 M

And,  The concentration of Br2 at equilibrium = 0.0955 M

The given chemical reaction at equilibrium is

2HBr(g) <=============>   H2(g) + Br2(g)

Initial conc. 0.50M 0M 0M

Conc. at equilibrium: (0.50 - 2x0.0955)M 0.0955M 0.0955M

= 0.309M

So,

Hence, [H2(g)] = 0.0955M, [Br2(g)] = 0.0955M

Now

[2HBr(g)] = 0.309 M

And, finally Kc can be calculated as

Kc = [H2(g)] x [Br2(g)] / [2HBr(g)]2  

= 0.0955M x 0.0955M / (0.309M)2  

= 0.0955

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