Question

The equilibrium between carbon dioxide gas and carbonic acid is very important in biology and environmental science. CO2 (aq) + H2O (l) → H2CO3 (aq) Which one of the following is the correct equilibrium constant expression (Kc) for this reaction?a. K =[H2CO3]/ [CO2]b. K=[CO2]/ [H2CO3]c. K=[H2CO3]/ [CO2][H2O]d. K=[CO2][H2O]/ [H2CO3]e. K=1/[H2CO3]

Answer 1

Answer:

The constant Kc is expressed as:

$Kc=\frac{[H_{2}CO_{3} ] }{[CO_{2}]*[H_{2}O] }$ (option C)

Explanation:

A dynamic equilibrium is a reaction that is never completed, since it occurs simultaneously in both directions (the reactants form products, and in turn, these again form reactants).

When the concentrations of each one of the substances that intervene (reagents or products) stabilize, that is, they are spent at the same rate as they are formed, the Chemical Balance is reached.

For the study of chemical equilibrium it is useful to use a value called equilibrium constant. The equilibrium constant depends on the temperature.

For any reaction, represented by the generic chemical equation:

aA + bB ⇔ cC + dD

the constant Kc is expressed by:

$Kc=\frac{[C]^{c} *[D]^{d} }{[A]^{a} *[B]^{b} }$

Then, the constant Kc is equal to the multiplication of the concentrations of the products raised to their stoichiometric coefficients by the multiplication of the concentrations of the reactants also raised to their stoichiometric coefficients.

So, in the case of:

CO₂ (aq) + H₂O (l) ⇄ H₂CO₃ (aq)

The constant Kc is expressed as:

$Kc=\frac{[H_{2}CO_{3} ] }{[CO_{2}]*[H_{2}O] }$ (option C)