Department of Chemistry, College of Science,
University of Santo Tomas,
España, Manila, 1015
August 24, 2012
A mixture can be homogenous or heterogenous, depending if the mixture has been uniform throughout the mixture or not. One of the objectives is to separate C10H8, NaCl and SiO2, and determine their percentages in the mixture. Since the mixture was not chemically combined, they can be separated by physical means. One can use a variety of techniques such as sublimation, selective dissolution, filtration or evaporation. As a result, the mixture contained 9.51% of C10H8, 16.2% of NaCl, and 60.40% SiO2.
A mixture is a combination of two or more pure substances in which each substance retains its own composition and properties. One easily recognized type of mixture is called a heterogenous mixture. Its portions contain different recognizable properties and are not uniform throughout the mixture. Another kind of mixture would be one with uniform properties throughout the mixture. It is called a homogenous mixture, also known as a solution (Whitten, 2011).
In this experiment, a mixture of C10H8, NaCl and SiO2 is involved. Since the components in this experiment are not chemically combined, they can be separated by simple physical means such as sublimation, selective dissolution, filtration and evaporation. Components can be separated based on the differences in their physical and chemical properties (Chang, 2008).
Sublimation is a process by which the molecules can escape directly from the solid to enter the gaseous state, bypassing the liquid state (Hein & Arena, 2011). Difference in vapor pressure allows one to sublime from the rest of the mixture. Vapor pressure is the pressure in the gaseous state (Joesten & Hogg, 2011). It is independent of the amount of liquid and vapor present, but it increases as the temperature increases (Hein & Arena, 2011).
Solubility is defined as the quantity of solute that will dissolve in a given amount of solvent at a given temperature. It is determined by the strength of the forces of attraction. The forces acting between the solvent and solute particles must be greater than those within the solute for the solute to dissolve, thus the phase “like dissolves like” comes in (Joesten & Hogg, 2011). Solubility is the principle behind selective dissolution. Selective Dissolution is the process of adding water and letting a substance dissolve in the solution. It is usually followed by filtration, a process of removing insoluble solids from water by passing the water through a permeable fabric or porous bed of materials while the suspended particles cannot. It is one of the most common techniques in separating components of mixtures.
Evaporation is the process by which molecules escape from the liquid to the gas phase, leaving it cooler than it was before they escaped (Hein & Arena, 2011). According to the 4th statement of Kinetic Molecular Theory, not all molecules in a liquid posses the same kinetic energy as some will have above-average kinetic energy and some will have below-average kinetic energy. This results from the collision between molecules since the energy of a given molecule constantly changes (Stoker, 2010). Substances that evaporate readily are said to be volatile (Hein & Arena, 2011). Boiling point is the temperature at which the vapor pressure equals the atmospheric pressure (Joesten & Hogg, 2011). This distinguishes which substance would evaporate first at a certain temperature, thus becomes the lying principle behind Evaporation.
With the use of separation techniques, this experiment aims to resolve the mixture into its component parts and to determine the percentages in the mixture.
One of the most...