In chemistry, an Arrhenius acid is a substance that increases the concentration of hydrogen ions (H⁺) in an aqueous solution.
Did you know that the lemon juice contains citric acid, a weak organic acid capable of donating up to three hydrogen ions (H⁺) per molecule in water?
Below is a super simple experiment to explore the concept of an Arrhenius acid in real life. We aim to prove that lemon juice is an Arrhenius acid and that when it is mixed with a base, it can react!
Lemon Juice & Baking Soda Experiment
Materials needed:
Fresh lemon or lemon juice (contains citric acid)
Baking soda (sodium bicarbonate)
A clear glass or container
Water
Spoon
Procedure:
Pour some lemon juice into the glass (or squeeze a fresh lemon).
Add a little water to dilute it—this simulates an aqueous solution.
Sprinkle a spoonful of baking soda into the lemon juice.
Observe the reaction
Observation: Fizzing and bubbling occur!
Why it works: When citric acid dissolves in water, the polar molecules of water interact with citric acid, an interaction that pulls apart the hydrogen atoms bonded to oxygen in the acid. It's a triprotic acid, meaning it can donate up to three hydrogen ions (H⁺) per molecule in water.
The hydrogen atoms, due to being tugged away by the water molecules, slowly lose their attachment with the citric acid molecule and become free-floating hydrogen ions (H+, protons) in solution. These newly formed H⁺ Ions make the solution acidic. But because it’s a weak acid, only a fraction of the citric acid molecules fully donate H⁺ ions. That’s why lemon juice has a sour taste but isn’t corrosive enough to burn your mouth like strong acids (e.g., hydrochloric acid).
The baking soda acts as a base, and the reaction produces carbon dioxide gas—hence the fizz! This release of gas is a direct result of acid-base neutralization.
Bonus Tip: Try comparing the reaction using vinegar or orange juice and notice differences in intensity—that's acidity in action!
Related Content – Three types of Acids in Organic chemistry