when 0.20 mole HF is dissolved in water to a volume of 1.00 L, 5.8% of the HF dissociates to form F- (aq). What is the equilibrium constant for the reaction ?
HF(aq) +H2O(l) ------ F- (aq) +H3O+ (aq)
I worked this below. Try one of your earlier posts. I can look for a link if you can't find it.
To find the equilibrium constant for this reaction, we need to know the concentration of each species at equilibrium. We can start by calculating the initial concentration of HF, which is given as 0.20 mole in a volume of 1.00 L.
Initial concentration of HF = 0.20 mol / 1.00 L = 0.20 M
Since 5.8% of the HF dissociates, we can calculate the concentration of F- by multiplying the initial concentration of HF by the dissociation percentage.
Concentration of F- = 0.20 M x 0.058 = 0.0116 M
Since water (H2O) is a liquid, its concentration remains constant and does not affect the equilibrium constant. Similarly, H3O+ is formed in the reaction but it is not provided with a concentration, so we cannot determine its value directly.
Now, to calculate the equilibrium concentration of HF, we need to subtract the concentration of F- from the initial concentration of HF:
Equilibrium concentration of HF = Initial concentration - Concentration of F-
Equilibrium concentration of HF = 0.20 M - 0.0116 M = 0.1884 M
Given the balanced equation: HF(aq) + H2O(l) → F-(aq) + H3O+(aq), we can see that the stoichiometric coefficient of HF is 1, and the stoichiometric coefficient of F- is also 1.
Now, the equilibrium constant expression for the given reaction is:
Kc = [F-][H3O+] / [HF]
Since the stoichiometric coefficients for both F- and HF are 1, the equilibrium constant can be simplified to:
Kc = [F-][H3O+] / [HF] = ([F-] * [H3O+]) / ([HF])
Given that the equilibrium concentrations are as follows:
[F-] = 0.0116 M
[H3O+] = unknown (we cannot determine this value directly)
[HF] = 0.1884 M
We can now substitute these values into the equilibrium constant expression to calculate Kc.
Kc = (0.0116 M * [H3O+]) / (0.1884 M)
Please note that without the concentration of H3O+, we cannot determine the exact value of the equilibrium constant. To further determine the value for Kc, you would need additional information.