Use the "x is small" approximation to find the concentration of the products in the following reaction which initially contains only 0.85 M HCN. Decide whether using the approximation was valid or invalid.HCN(aq) ⇌ H+(aq) + CN−(aq), Kc= 6.17 x 10−10

Respuesta :

Answer:

Concentration of product at equilibrium ;

[tex][H^+]=0.0000229 M[/tex]

[tex][CN^-]=0.0000229 M[/tex]

Explanation:

[tex]HCN(aq)\rightleftharpoons H^+(aq) + CN^-(aq)[/tex]

initially

0.85 M        0    0

(0.85-x)M    x      x

The equilibrium constant of reaction = [tex]K_c= 6.17\times 10^{-10}[/tex]

The expression of an equilibrium cannot can be written as:

[tex]K_c=\frac{[H^+][CN^-]}{[HCN]}[/tex]

[tex]6.17\times 10^{-10}=\frac{x\times x}{(0.85-x)}[/tex]

Solving for x:

x = 0.0000229

Concentration of product at equilibrium ;

[tex][H^+]=0.0000229 M[/tex]

[tex][CN^-]=0.0000229 M[/tex]

The approximation is valid because [tex]K_c[/tex] is very small.

The concentration of the product at Equilibrium is shown on attached image.

Calculation of  concentration:

Since

0.85 M        0    0

(0.85-x)M    x      x

Now the value of x should be

[tex]6.17 \times 10^{-10} = \frac{x\times x}{(0.85-x)}[/tex]

x = 0.0000229

So based on this, the above concentration should be determined.

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Ver imagen andromache