Question

Describe how to calculate the Ka,for the reaction of water with HF. Please explain like I was a 9 year old. ;/ I just need to understand why 7.2x10-4...

Answer 1

first write the reaction when HF added to water

HF + H2O ----------> H3O⁺  + F^-

as HF is acid we use Ka instead of K

Ka signifies acid dissociation constant

Ka = concentration of products / concentration of reactants

Ka = [H3O⁺][F^-]/ [HF]   

H2O we will not include in equilibrium expression. pure solids and liquids we eliminate from equilibrium

if you know H⁺  of F^-  we can find the Ka by substituting in above expression.

Ka of HF = 7.2 x 10^-4  is standard value measured experimentally base on how much HF can be dissociated.