“hydrochloric acid, hcl, is a strong acid that dissociates completely in water to form h3o+ and cl–. should the value of k for the reaction hcl(aq) + h2o(l) ⇄ h3o+(aq) + cl–(aq) be 1 × 10–2, 1 × 10–5, or “very large"?

 Very Large

Explanation:  The measure of the acidity can be described by how much the acid is willing to lose its proton or better say, positive species and thereby making its conjugate base much stable.

Thus HCl is indeed a strong acid as Cl^{^{-}} is a very stable conjugate base .

Its dissociation in aqueous solvent can be written as -

              HCl(aq)  +  H2O(l)    ⇄   H3O+(aq)  +  Cl–(aq)

Its dissociation constant K mathematically can be written as

                            K=     [H3O+]  [Cl-]

                                     [HCl]  [H2O]

Disscoaition constant is also known as Acid Ionization constant, used to measure the strenghth od an acid .

Thus , HCl, being a strong acid will have large amount of the dissociation constant.