The identification of acids and bases using a natural indicator Purpose: The purpose of this lab practice is to identify the pH of certain solutions and if they are acids or bases. Introduction: In chemistry, pH is a measure of the activity of the (solvated) hydrogen ion. p[H], which measures the hydrogen ion concentration, is closely related to, and is often written as, pH. Depending on the pH solutions will be acids or bases. An acid is a chemical compound that dissociates in solution, releasing hydrogen ions and lowering the solution pH (a proton donor). An acidic solution has a pH below 7. Acids can be strong acids which ionize completely in aqueous solution or weak acids which ionize partially. A base is a substance that combines with acids to form salts; a substance that dissociates to give hydroxide ions in aqueous solutions; a substance whose molecule or ion can combine with a proton (hydrogen ion); a substance capable of donating a pair of electrons (to an acid) for the formation of a coordinate covalent bond. Bases can be strong bases which are able to dissociate completely in water or weak bases which dissociate partially.
In this practice we use natural indicators, which are pH indicators in the form of plant pigments known as antocyanines which change color over different pH ranges and depending on source for the pH.
Neutralization is a chemical reaction in which a base and an acid react to form a salt.
DroppersHidrion paperRed Cabbage indicatorMilkBleachYogurt Microplate| VinegarEasy OffMg (OH) WaterMuriatic acidBeakersDetergent S/M|
1. Open the dropper, put the ph strip inside the bottle, analyze the pH of the substance according to this table:
2. Put 5 drops on the microplate of each of the substances and 3 drops of the natural indicators and watch the change in the color.
| Hidrion Paper| Red cabbage indicator|
Substance| Color| pH| Color| pH|