2HCl(g) ⇌ H2(g) + Cl2(g) 평형상수 3.2×10^(-34)

2HCl(g) ⇌ H2(g) + Cl2(g) 평형상수 3.2×10^(-34)

 

 

The reaction 2HCl(g) ⇌ H2(g) + Cl2(g) has a K = 3.2×10^(-34) at 25℃.

If a reaction vessel containing 2.00 M HCl is allowed to come to equilibrium,

what will be the equilibrium concentrations of H2 and Cl2?

 

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K = [H2][Cl2] / [HCl]^2

 

 

ICE 도표를 작성하면,

 

........... 2HCl(g) . ⇌ . H2(g) . + . Cl2(g)

초기(M) ... 2.00 ......... 0 ......... 0

변화(M) ... -2x .......... +x ........ +x

평형(M) ... 2.00-2x ...... x ......... x

 

 

K = [H2][Cl2] / [HCl]^2

3.2×10^(-34) = x^2 / (2.00-2x) = x^2 / 2.00

( K 값이 매우 작기 때문에, (2.00-2x) ≒ 2.00 로 근사 가능. )

 

x = [3.2×10^(-34) × 2.00]^(1/2)

= 2.53×10^(-17)

 

 

답: 2.53×10^(-17) M

 

 

 

[ 관련 예제 ]

Q. The reaction 2HCl(g) ⇌ H2(g) + Cl2(g) has a K = 3.2×10^(-34) at 25℃.

If a reaction vessel initially contains 0.0500 M of HCl and then reacts to reach equilibrium, what will be the equilibrium concentrations of HCl, H2 and Cl2?

A. [HCl] = 0.0500 M, [H2] = [Cl2] = 4.00×10^(-18) M

x = [3.2×10^(-34) × 0.0500]^(1/2) = 4.00×10^(-18)