Lab Final

Question 1

Vacuum Filtration

Answer 1

used to isolated a solid from a liquid-solid mixture and to remove solid impurities from a large quantity of liquid

Question 2

Filter trap

Answer 2

usually between a filter flask and water aspirator to keep water from backing up into the flask.

Question 3

Gravity filtration

Answer 3

used to remove solid impurities from a liquid or solution
the liquid component drains through a filter paper by gravity, leaving the solid on the paper
often used to remove drying agents and solid impurities from recystallization

Question 4

liquid-liquid extraction

Answer 4

Based on the principle that if a substance is soluble to some extent in two immiscible liquids, most of it can be transferred from one liquid to the other by a process that involves thorough mixing of the liquids

Question 5

Evaporation

Answer 5

conversion of a liquid to vapor at or below the boiling point of the liquid
used to remove a volatile solvent

Question 6

Recrystallization

Answer 6

Used to purify organic solids

dissolve a solid that had already crystallized and cause it to again recrystallize

Question 7

melting point

Answer 7

the temperature at which the solid and liquid phases of a substance are in equilibrium at 1 atm
can be used to characterize organic compounds and assess their purity

Question 8

Reflux

Answer 8

Boiling a reaction mixture and condensing the solvent vapors back into the reaction vessel
Water is against gravity

Question 9

Boiling chips

Answer 9

prevents bumping (violent eruptions as superheated bubbles are discharged) by providing nucleating sites on which smaller bubbles can form.

Question 10

Condenser

Answer 10

used in reflux - returns solvent vapors to the reaction vessel so that no solvent is lost

Question 11

Distillation

Answer 11

The process of vaporizing a liquid mixture in one vessel and condensing the vapors into another

Question 12

Simple distillation

Answer 12

involves only a single vaporization-condensation cycle
Useful for purifying a liqiuid that contains either nonvolatile impurities or small amounts of higher or lower boiling impurities
traditional apparatus includes a condenser; compact does no

Question 13

Washing liquids

Answer 13

similar to liquid-liquid extraction, but washing removes impurities from a desired substance

Question 14

drying liquids

Answer 14

drying agent is used to remove traces of water before evaporation and distillation are carried out

Question 15

gas chromatography

Answer 15

method of separation and analysis of volatile components of mixtures

Question 16

retention time

Answer 16

time it takes for a component to pass through the gas chromatography column
depends on its relative concentration

Question 17

Fractional Distillation

Answer 17

distillation process that inolves several concurrent vaporization-condensation cycles
distillate usually collected in several separate fraction collectors over a different temperature range

Question 18

addition

Answer 18

uses a separatory funnel
add a reactant over the course of the reaction
necessary for very exothermic reactions or if one reactant must be kept in excess to prevent side products

Question 19

Sublimation

Answer 19

solid passes directly into the vapor phase
no solvent required and losses in transfer is low
the solid is heated to a vapor, vapor is condensed on a cold surface, and the condensed solid is scraped off

Question 20

boiling point

Answer 20

the temperature at which the vapor pressure of the liquid is equal to the external pressure at the surface of the liquid
used to assess the substance and its purity

Question 21

Refractive index

Answer 21

the ratio of the speed of light in a vacuum to its speed in the substance
unique physical property that can be measured with great accuracy, so useful for characterizing organic substances