when Fe(NO3)3 and KNCS were mixed they reacted together to establish an equilibrium with FE(NCS)+2.
what are the changes in terms of quotient Q when the solutions were just mixed (no reaction), to the point where equilibrium is reached.
To determine the changes in terms of the quotient Q when the solutions are mixed and when equilibrium is reached, we need to understand the initial and equilibrium conditions of the reaction.
Initially, when the solutions of Fe(NO3)3 (iron(III) nitrate) and KNCS (potassium thiocyanate) are mixed, there is no FE(NCS)+2 (iron(III) thiocyanate) present. So, the initial concentrations of Fe(NCS)+2, [Fe(NCS)+2], is zero.
However, there are Fe3+ (iron(III)) and NCS- (thiocyanate) ions present in the reaction mixture. The initial concentrations of Fe3+ and NCS- are determined by the concentration of the starting solutions, Fe(NO3)3 and KNCS, respectively.
When the reaction proceeds, the reactants Fe3+ and NCS- combine to form the product Fe(NCS)+2 until an equilibrium is established. At equilibrium, the forward and reverse reactions occur at the same rate, resulting in the formation of a dynamic state where the concentrations of all species involved in the reaction remain constant.
Now, consider the equilibrium expression for the reaction:
Fe3+ + NCS- ⇌ Fe(NCS)+2
The equilibrium constant expression, K, is given by the ratio of the products' concentrations raised to their stoichiometric coefficients divided by the reactants' concentrations raised to their stoichiometric coefficients.
K = [Fe(NCS)+2] / ([Fe3+] * [NCS-])
Initially, since [Fe(NCS)+2] = 0, the value of Q (the reaction quotient) will be zero, as it is the ratio of products to reactants.
As the reaction proceeds, Fe(NCS)+2 is formed until equilibrium is reached. At equilibrium, the forward and reverse reaction rates are equal, and the concentrations of all species remain constant.
At equilibrium, Q becomes equal to the equilibrium constant (K). This means that the value of Q will reach the same numerical value as K. The concentration of Fe(NCS)+2 is no longer zero, and the concentrations of Fe3+ and NCS- are determined by the equilibrium conditions.
So, the change in terms of the quotient Q is from an initial value of 0 (when the solutions were just mixed) to the equilibrium value, which is equal to the equilibrium constant K when the system reaches equilibrium.