Purpose: Every chemical has a set of defined physical properties, and when combined they present a unique fingerprint for that chemical. When chemicals are present in a mixture, these unique physical properties can be utilized to separate the chemicals into their pure states. This experiment will give you experience in separating the components in a three-compound mixture; ammonium chloride, sodium chloride (table salt), and silicon dioxide (sand).
Background: Because there are 3 components in our mixture, we will need several techniques to separate them. For this particular exercise, you should be familiar with the following:
· Sublimation: Many chemicals will sublime (phase change from solid state to gas state) he easiest way to accomplish this is to hold a glass stir rod against the lip of the container containing the solid and liquid, and gently pour the liquid down the stir rod into a new container. · Extraction: Extraction is a way to separate two components with different solubilities, that is, extract one chemical from another. Extraction relies on a principle called serial dilution.
Imagine a mixture of small plastic beads and sugar. They can’t be separated easily as solids unless you want to physically pick through the particles with a pair of tweezers. However, sugar will dissolve in water and the plastic won’t. If we add water to the mixture, we can then pour off the sugar-water from the plastic beads (that is, decanting the solution). However, there will still be some sugar-water left around the beads. We can add more water to the beads, diluting the sugar-water that was left, and decanting again. If we do this several times (three times is typically sufficient) we remove essentially all of the sugar from around the plastic beads. The adding of water