Question

A reaction begins with 1.00 mol of HCl in a 4.00 liter container at a certain temperature.

Answer 1

Answer:

$[HCl]_{eq}=0.05M$

Explanation:

Hello,

In this case, for the given chemical reaction, the law of mass action at equilibrium results:

$Kc=\frac{[H_2]_{eq}[Cl_2]_{eq}}{[HCl]^2_{eq}}$

Next, in terms of the change $x$ due to reaction extent, it is rewritten, considering an initial concentration of HCl of 0.25M (1mol/4L), as:

$4.00=\frac{(x)(x)}{(0.25-2x)^2}$

Thus, solving for $x$ via quadratic equation or solver, the following results are obtained:

$x_1=0.1M\\x_2=0.17M$

Clearly, the solution is $x=0.1M$ as the other result will provide a negative concentration for the hydrochloric acid at equilibrium, thereby, its equilibrium concentration turns out:

$[HCl]_{eq}=0.25M-2*0.1M$

$[HCl]_{eq}=0.05M$

Best regards.