Based on VSEPR theory, the number of 90 degree F-Br-F angles in BrF₅ is

The species which by definition has ZERO standard molar enthalpy of formation at 298 K is

Among the following, the intensive property is (properties are)

Aqueous solution of HNO₃, KOH and CH₃COOH and CH₃COONa of identical concentrations are provided. The pairs of solutions which form a buffer upon mixing is(are)