Lemonade is acidic, which is caused by the high amount of citric acid in lemons. This is consistent with what we taste on the tip of our tongue. Lemonade generally refers to lemon juice, which is a mixture of acids such as citric acid and sodium salts such as sodium citrate. The mixture is acidic because citric acid has a low pKa, its first pKa is 3.1, so an equal mixture of acid and conjugate base has a pH = 3.1. Typically lemonade has a pH between 2 and 3, indicating that it is a highly acidic substance.