Red cabbage juice is a good indicator of pH because it contains flavin, a pigment molecule that changes colors according to the concentration of hydrogen ions in a solution. The juice is prepared by soaking chopped red cabbage in boiling water for at least 10 minutes and then filtering the solution to eliminate any plant material.Know More
The prepared red cabbage juice is red, purple or blue, depending on the pH of the water used in its preparation. The addition of lemon juice, an acid, lowers the pH and causes the juice to become red. The addition of ammonia, a base, raises the pH and causes the juice to turn blue. The addition of stronger bases raises the pH higher and the solution becomes green or yellow, depending on the strength of the base.
Scientists use pH to measure the acidity of a material. A low pH indicates a high hydrogen ion concentration and a high pH indicates a low concentration. At a pH of 7, the concentration of hydrogen and hydroxyl ions are equal, resulting in a neutral solution. Students can soak filter paper in the juice solution, allow it to dry, and then cut it into strips to create a portable pH indicator that allows them to test pH outside the lab.Learn more about Acids & Bases
When the pH of a solution is equal to the pKa, the buffer is in its most effective state. In this state, the concentration of the conjugate base is equal to that of the acid, allowing it to effectively neutralize added strong acid or base and maintain a desired pH. For a desired pH different than the pKa, the ratio of the base to the acid is modified.Full Answer >
In titration experiments, the standard solution is the solution of an acid or base whose concentration is accurately known. The standard solution is used to neutralize an acid or base of unknown concentration.Full Answer >
In chemistry, a buffer is a substance that is able to resist changes in pH when it is a part of a solution. Buffers are added to solutions to resist acidic or basic compounds.Full Answer >
A buffer zone in chemistry is a region where the pH of a solution remains constant. In an acid-base titration of a weak acid with a strong base, the pH of the solution increases, levels off through the buffer zone and then increases quickly to reach the equivalence point.Full Answer >