Why are ionic reactions very fast in aqueous medium?
Water has a permanent dipole character, which means it has a slight positive and negative charge permanently in it (due to electronegativity difference). So, in case of an ionic reaction, it helps in easier solvation of ions by pulling them with its charged centres (positive centre attracts negative ions and negative centre attracts positive ions)
Aqueous is a term specially for water as a solvent. Any polar solvent can support ionic reactions.