Quantitative Analysis Exam 3

Activity Coefficient

Measure of the extent to which the ionic strength of a solution influences an equilibrium

unity

The activity of an uncharged molecule, no matter the level of ionic strength

salt effect

adding an inert electrolyte changes the behavior of ions in solution by modifying their effective concentration (activity) through charge screening.

ionic strength

measure of concentrations in an ion (strength of bonds plays a big role)

ideal

activity coefficient is 1, same properties as ideal gas

non-ideal

activity coefficient is between 0-1

hydrated

water molecules line the perimeter of the ion/cell

ionic

composed of ions

separation

isolate the analyte from other analytes and/or interfering constituents—-goal is to eliminate the reduce interferences so that quantitative and qualitative information can be obtained

extraction

a method in which you take advantage of an analyte’s preference of one phase over another based on chemical affinities (organic phase vs aq phase)

ion exchange

different molecules (ions) get swapped or changed

immiscible

two solvents cannot mix (oil and water)

miscible

two solvents that can mix (water and juice)

stationary phase

fixed solid/liquid stuff in the column that the other stuff runs through (the resin)

mobile phase

The liquid stuff that runs through the stationary phase (NOT the other liquid added that you are testing)

eddy diffusion

peak broadening due to multiple flow paths through a packed bed of stationary heterogenous particles

longitudinal diffusion

peak broadening occurs due to diffusion of individual analyte molecules in the mobile phase in the direction of the column

resistance to mass transfer

depends on how quickly the analyte can move back and forth between the mobile phase and stationary phase, every transition back and forth requires energy. The quicker the analyte can partition, the smaller this term.

Le Chatelier Principle

principle used to predict the effect of a change in conditions on chemical equilibrium.

Activity

related to concentration by a dimensionless factor called the activity coefficient, the concentrations that is actually participating in chemistry or doing work

Extended Debye-Huckel equation

activity coeffiecient equation (-log gamma x)

electrolytes

can affect activity of ionic species, the effect of added electrolyte is independent of chemical nature of the electrolyte but on the ionic strength

retention factor

degree of retention of a specific analyte

selectivity factor

ability of the column (chromatography) to chemically distinguish between sample and components

column efficiency

related to the width of the gaussian peaks (H)