Mcat Organic Chemistry Ch. 12 Separations & Purifications

Acid-base properties can be used to increase solubility by dissolving an acid in a base and a base in an acid. Aqueous Phase is the polar (water) layer that dissolves compounds with hydrogen bonding or polarity. Organic Phase is the nonpolar layer that dissolves nonpolar compounds.

In solubility-based methods, the wash process involves running a small amount of solute that dissolves impurities over the compound of interest, which is the reverse of extraction. This helps in removing impurities without affecting the compound of interest.

Filtration in solubility-based methods is specifically used to separate a solid from a liquid mixture, with the solid being collected on the filter paper while the liquid passes through.

Gravity filtration in solubility-based methods relies on the solvent's weight to pass through the filter, particularly used when the product of interest is in the filtrate. Hot solvent is used to maintain solubility. Therefore, incorrect answers suggesting crystallization aiding filtration, active pumping by the filter, or preference for cold solvent are inaccurate in this context.

Vacuum Filtration is a technique used to separate solids from liquids efficiently. The correct answer describes the process accurately, while the incorrect answers provide misleading information regarding the separation method.

Recrystallization involves dissolving the product in a minimal amount of hot solvent to separate impurities which are more soluble. As the solution cools, the product crystals form while excluding impurities, leading to a purified product.

Distillation separates liquids based on their boiling points where the liquid with the lowest boiling point vaporizes first. The process is specifically designed to separate substances based on this principle.

Simple distillation is an effective method when the boiling points of the substances involved are relatively close but still have a significant difference. The range of 25 oC ensures efficient separation during the process.

Vacuum distillation is specifically used when the boiling points of the products are over 150oC to prevent degradation. It is not limited to liquids below 100oC, or products close to room temperature. The use of vacuum is crucial in this method to lower ambient pressure and reduce the vapor pressure required for boiling.

Fractional Distillation is a method used for separating liquids based on their boiling points by taking advantage of the differences in boiling points between the liquids. It allows for a refined separation of liquids that have boiling points that are close together.

Chromatography involves the use of both a stationary phase (adsorbent) and a mobile phase to separate compounds based on their physical or chemical properties. The stationary phase is typically a polar solid, while the mobile phase is usually a liquid or gas that runs through the stationary phase to elute the sample.

Retardation Factor (Rf) in chromatography-based methods represents the relative movement of compounds based on their affinity for the stationary and mobile phases, leading to their separation through partitioning.

Partition Chromatography, Gel Permeation Chromatography, and Capillary Electrophoresis are not types of chromatography-based methods. Therefore, they are incorrect answers.

In Thin-Layer & Paper Chromatography-based methods, the stationary phase is typically a polar material like silica, alumina, or paper, while the mobile phase is a nonpolar solvent. This setup allows for the separation and analysis of compounds based on their relative polarities. Reverse-Phase Chromatography involves using a nonpolar stationary phase and a polar solvent for separation.

Column chromatography relies on the principles of polarity, size, or affinity to separate compounds, and the stationary phase in the column usually contains silica or alumina beads. The mobile phase, a nonpolar solvent, moves through the column via gravity to facilitate separation.

Ion-Exchange Column Chromatography works by utilizing the opposite charges between the stationary phase beads and the compounds being separated, allowing them to bind together and be separated based on their charges.

Size-Exclusion Column Chromatography separates molecules based on their size by utilizing beads of stationary phase with small pores to selectively trap smaller compounds while allowing larger compounds to travel through faster.

Affinity Chromatography works on the principle of specific interactions between a compound of interest and a receptor or antibody coated on the stationary phase, leading to selective retention and separation of the compound from the sample.

The purpose of Gas Chromatography is to separate vaporizable compounds based on how well they adhere to the adsorbent in the column with a stationary phase of crushed metal or polymer and a mobile phase of a nonreactive gas. It may also be combined with mass spectrometry to determine molecular weight or structure.

High-Performance Liquid Chromatography is a method that involves using computer-mediated solvent and temperature gradients. It is not a form of gas chromatography, thin-layer chromatography, or paper chromatography.