MDCAT Acids, Bases & Salts 2026

Three Definitions

• Arrhenius — acid releases H⁺; base releases OH⁻ in water.
• Brønsted-Lowry — acid is a proton donor; base is a proton acceptor.
• Lewis — acid is an electron pair acceptor; base is a donor.

pH & Useful Relations

• pH = −log[H⁺]; pOH = −log[OH⁻]; pH + pOH = 14
• K_w = [H⁺][OH⁻] = 10⁻¹⁴ at 25°C
• Strong acid in water: pH = −log(conc.)

Pair with Chemical Equilibrium.