Explanation:
If we have the following reaction at equilibrium:
<em> aA + bB ⇄ cC + dD</em>
where a, b, c, and d are the stoichiometric coefficients for the reacting species A, B, C, and D. For the reaction at a particular temperature:
Kc=([C]^c *[D]^d)/([A]^a *[B]^b)
where Kc is the equilibrium constant, which holds that <em>for a reversible reaction at equilibrium and a constant temperature, a certain ratio of reactant and product concentrations has a constant value, Kc</em> (the equilibrium constant). Note that although the concentrations may vary, as long as the reaction in in equilibrium and temperatura don't change, the value of <u>K remains constant.</u>
For reactions that have not reached equilibrium, we obtain the reaction quotient (Qc), instead of the equilibrium constant <u>by substituting the initial concentrations into the equilibrium constant expression.</u>
Qc=([Co]^c *[Do]^d)/([Ao]^a *[Bo]^b)
To determine the direction in wich the net reaction will proceed to reach equilibrium, que compare the values of Qc and Kc.
- Qc < Kc: To reach equilibrium, reactants must be converted to products (→)
- Qc = Kc: The initial concentrations are equilibrium concentrations. The system in at equilibrium.
- Qc > Kc: To reach equilibrium, products must be converted to reactants (←)
Solution:
We have the following reaction:
NO2Cl(g)+NO(g)⇌NOCl(g)+NO2(g)
So:
Kc=([NOCl]^1*[NO2]^1)/([NO2Cl]^1 *[NO]^1)
=([NOCl][NO2])/([NO2Cl][NO])
1. In the equation above, [NO2Cl] it's in the denominator, so if we increase it's numericall value by adding NO2Cl <u>decreases Qc to a value less than Kc.</u>
<em>(From the chemical point of view, if we disturb the equilibrium adding NO2Cl (a reactant), to reach equilibrium again the system proceeds from left to right (→) consuming this reactant.)</em>
2. To reach a new state of equilibrium (<em>where Qc = Kc</em>), Qc therefore increases wich means that the denominator of the expression for Qc decreases <em>(in order to increase the denominator as mention above).</em>
3. To accomplish this, the concentration of reageants decreases <em>(reagents are being consumed), </em>and the concentration of prodcuts increases <em>(products are being formed).</em>
