Uploaded April 2015 | Updated September 2026, 1 week ago
Learn about how to write equilibrium constant expressions and interpret their meaning in this video!
Learn about how to write equilibrium constant expressions and interpret their meaning in this video!










![Titrations
Learn about the basics of titrations and the steps to perform them in this video!
transcript
when a strong acid and a strong base are mixed together, a neutralization reaction occurs. They end up forming water and a salt. at the end of the reaction, if the molar ratio of reactants was balanced, we’ll get a solution with a pH of 7, neutral.
When an acid and base are mixed, the equivalence point is when the number of moles of hydrogen ions equals the number of moles of hydroxide ions. with strong acids and bases reacting, the reaction produces a neutral solution with a pH of 7.
when we do a titration where we add an acid or base with a known concentration, called the standard solution, to a base or acid with an unknown concentration, we need a way to know when the equivalence point has been reached. to do this we use an indicator.
Indicators are often used to determine when enough of the standard solution has been added to neutralize the acid or base. the indicator needs to change color near the equivalence point.
The point at which the indicator changes color is the end point of the titration. the end point is not the same as the equivalence point, but it’s usually very near it on the pH scale.
A measured volume of an acid solution of unknown concentration is added to a flask. Then several drops of the indicator are added to the solution while the flask is gently swirled. Then measured volumes of a base of known concentration are mixed into the acid until the indicator just barely changes color.
the equivalence point (equal [H+] and [OH-]) is not exactly the same as the end point. The end point is where the indicator changes color. The standard solution should change the indicator color so that the end point can be determined. You want to see the color change usually just after the equivalence point has been reached. for example, phenophthalein turns pink with a base around a pH of 8, so the end point of a titration with a base will be measured when the solution just turns pink. Titrations](https://i.ytimg.com/vi/FJzpVxWK4c8/mqdefault.jpg)