Answer:
HCl is the correct answer
HSDB and the SRC Physical Properties database database reports that propionic acid has a water solubility of 1000 g/l at 25 °C. Ullmann and Knovel Solvents - A Properties Database reports that propionic acid is miscible in any ratio with water.
See if the carbon atoms are SP2 or Sp they the coplanirty is more and if its Sp3 hybridization it cant be in coplanar as Sp3 is having Td shape where as sp2 and sp are not :)
The answer is A. The pH decreases
they are both types of measurements
