For each of the following reactions, predict whether the equilibrium lies predominantly to the left or to the right.
HCN(aq) + SO42-(aq) CN -(aq) + HSO4-(aq)
I think it has something to do with the Ka but im not sure!
This requires a little imagination.
If I call k1 = Ka for HCN it will be
HCN ==> H^+ + CN^-
k1 = Ka for HCN = (H^+)(CN^-)/(HCN)
k2=Ka2 for H2SO4 HSO4^- ==> H^+ + SO4^-
k2 = (H+)(SO4^2-)/(HSO4^-) but I want the reverse of this; therefore,
1/k2 = (HSO4^-)/(H^+)(SO4^2-)
HCN + SO4^- ==> HSO4^2- + CN^-
k1*(1/k2) = [(H^+)(CN^-)/(HCN)]*[(HSO4^-)/(H^+)(SO4^2-)] and this leaves
(CN^-)((HSO4^-)/(HCN)(SO4^2-) which is Keq for the reaction you started with.
So k1*(1/k2) = look in you book for k1 and k2. My text lists (but you want the use the ones listed in your text) = 1E-9/0.012 = about 8E-8 which tells you that the reactants are favored. That is, the equilibrium lies (far) to the left.
thanks! also for this question Calculate the hydronium ion concentration and pH in a 0.037 M solution of sodium formate, NaHCO2.
hydronium ion concentration I made an equation: k=x^2/.037-x but when i look up the k what compound am i looking for? how do i know?
If you wrote the hydrolysis equation (the one form Kb formate) you would know.
........HCO2^- + HOH ==> HCOOH + OH^-
Kb(for formate) = (Kw/Ka for HCOOH) = (x)(x)/(HCO2^-) and solve for x = OH^- then convert to pH. Don't forget this is OH you're solving for, not H^+.
To predict whether the equilibrium favors the left or the right, we can use the concept of equilibrium constants. In this case, you're correct that the Ka (acid dissociation constant) can be helpful.
Let's break down the given reaction: HCN(aq) + SO42-(aq) ⇌ CN-(aq) + HSO4-(aq)
The reaction involves the dissociation of the acid HCN and the dissociation of the salt SO42-. The equilibrium constant for this reaction, denoted as Keq, is given by the ratio of the concentrations of the products to the concentrations of the reactants, each concentration raised to the power of its stoichiometric coefficient.
For our reaction, the equilibrium expression can be written as:
Keq = [CN-] [HSO4-] / [HCN] [SO42-]
If the value of Keq is greater than 1, the equilibrium favors the products (right side). If the value of Keq is less than 1, the equilibrium favors the reactants (left side). If the value of Keq is approximately 1, it suggests that both reactants and products are present in significant amounts.
To determine the equilibrium position, you would need specific values for the concentrations of reactants and products, as well as the value of the equilibrium constant.
Since we do not have specific values, we cannot make a definitive prediction about the equilibrium position in this case. However, if you are given the Ka values for HCN and HSO4-, you could use these values to calculate the equilibrium constant Kc, which is related to Ka.
Kc = Ka(CN-) / Ka(HCN) * Ka(HSO4-) / Ka(SO42-)
By calculating Kc, you can evaluate if the equilibrium favors the products (right side) or the reactants (left side).
Note: The explanation above assumes temperature remains constant.