Separation of the Components of a Mixture AP Chem Lab.
Separation of the Components of a Mixture
I. Purpose: The purpose of this lab is to become familiar with the methods of separating mixtures. This experiment separates a mixture of NaCl, NH4Cl, and SiO2 by using decantation, extraction, and sublimation. Our mixture was unknown sample 3.
II. Pre-Lab Questions:
1. Classify each of the following as a pure substance or a mixture; if a mixture, state whether it is heterogeneous of homogeneous: (a) concrete, (b) tomato juice, (c) marble, (d) seawater, (e) iron.
(a) concrete – heterogeneous mixture
(b) tomato juice – homogeneous mixture
(c) marble – heterogeneous mixture
(d) seawater – homogeneous mixture
(e) iron – pure substance
2. Suggest a way to determine whether a colorless liquid is pure water or a salt solution without tasting it. The solution should be heated so the water can evaporate. If it is a salt solution, the salt will be left behind as a solid when the water evaporates.
3. What distinguishes a mixture from an impure substance? A mixture is a combination of two or more substances in which each substance retains its own chemical identity and properties. An impure substance is a mixture in which one of the substances is preponderant (the amount of that substance far exceeds the amounts of other substances in the mixture).
4. Define the process of sublimation. Sublimation is the process in which a solid passes directly to the gaseous state and back to the solid state without the appearance of the liquid state.
5. How do decantation and filtration differ? Which should be faster? Decantation is the process of separating a liquid from a solid by gently pouring away the liquid. Filtration does this by passing the whole mixture through a porous substance (filter) which allows the liquid to pass through but not the solid. Filtration should be faster.