Input (grade 7): Lemon juice is about 5% to 6% (approximately 0.3 M) citric acid, which gives lemons a sour taste, and a pH of 2-3. This makes lemon juice an inexpensive, readily available acid for use in educational science experiments.
Output (grade 3): Lemon juice is about 5% citric acid, and has a pH of 2 to 3.