Which of the following species act as Lewis acids but CANNOT function as Bronsted-Lowry acids? — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

Lewis acids are electron-pair acceptors, whereas Bronsted-Lowry acids are proton donors. $BF_3$, $AlCl_3$, and $SnCl_4$ have empty orbitals (incomplete octet or vacant d-orbitals) to accept electrons, making them Lewis acids. However, they lack hydrogen atoms to donate as protons, so they are not Bronsted acids. $NH_4^+$ acts as a Bronsted acid by donating a proton.