University of Dayton - Chemistry 123 Lab Test Two 2019

Lab 4 (Title)

Introduction to Spectrophotometry

(Lab 4) Analyte

The chemical species being analyzed in the solution. (In this case, the analyte is the chemical species that interacts with light and is the solute of the solution)

(Lab 4) Transmittance

"T" - The ratio of the intensity of light reaching the detector, "I", to the intensity of light from the source I (initial). This is a detected quantity

(Lab 4) Percent Transmittance

"%T" is the percentage of source light intensity reaching the detector

(Lab 4) Absorbance

"A" is a measure of the light absorbed by the analyte and is calculated from the transmittance or percent transmittance

(Lab 4) Blanking Instrument

When the spectrophotometer used only has one detector, it is necessary to measure the intensity of light originating form the source prior to placing the sample in the sample cell

(Lab 4) Cuvet

Sample holder | Made of a disposable plastic and has an analysis width of 1.00cm | Important that there are not air bubbles, no fingerprints or scratches on the surface of the cuvet and that the cuvet be dry.

(Lab 4) Absorption Spectrum

The plot relating the quantity of light absorbed by a sample to the wavelength of the light / Created by scanning a sample through a range of wavelengths and measuring the intensity of light reaching the detector at each wavelength

(Lab 4) Absorbed

The peak in the spectrum representing wavelengths of light being absorbed by the analyte sample "Wavelengths 350nm - 480nm are being absorbed"

(Lab 4) Transmitted

The wavelengths not contained in the peak are the wavelengths being transmitted through the sample solution "Wavelengths from 300nm - 450nm and 480nm - 600nm are being transmitted"

(Lab 4) Beer-Lambert Law

A solution at a given wavelength of light is directly proportional to the concentration of a solution (A = Ɛbc) A = absorbance | Ɛ = molar absorptivity (L/mol*cm) | b = path length (cm) | c = concentration (mol/L)

(Lab 4) Sandards

When a set of known concentration solutions, standards, are available a calibration curve can be constructed

(Lab 4) Calibration Curve

A plot relating the concentration of a solution to its absorbance at a specific wavelength, usually at a wavelength where the analyte absorbs the most

Lab 5 (Title)

Spectrophotometric Determination of Stoichiometry

(Lab 5) Stoichiometry

The mole ratio of the substances in the reaction | is represented by the coefficients in the balanced chemical equation

(Lab 5) Ligand

The reactant that binds to the metal cation | the product of the reaction is a charged metal complex that remains in solution

(Lab 5) Coordination Complex

A type of charged metal-organic | Intense color allows for the investigation of the stoichiometry using spectrophotometry

(Lab 5) Complex Ion

The charge on the complex ion allows for high solubility in aqueous solutions

Lab 6 (Title)

Exploration of the Ideal Gas Law

(Lab 6) Ideal Gas Law

PV = nRT

(Lab 6) 1st Relationship

Temperature and Pressure

(Lab 6) 2nd Relationship

Mass and Pressure

(Lab 6) 3rd Relationship

Pressure and Volume

Lab 7 (Title)

Enthalpy of a Reaction - An Application of Hess's Law

(Lab 7) Hess's Law

Because reaction enthalpy is a state function, the enthalpy change of a series of reactions can be combined to determine the enthalpy change of a reaction that is the sum of the components of the series

(Lab 7) Why Coffee Cup Calorimetry?

1) Constant Pressure
2) Good Insulator

(Lab 7) Percent difference (Enthalpy of reaction to the experimental value)

[(Reaction Enthalpy)-(Experimental Enthalpy)] / [(Experimental Enthalpy)]

(Lab 7) Exothermic

Heat transferred from the system to the surroundings is negative (-)

(Lab 7) Endothermic

Reaction in which heat is transferred into the system form the surroundings is positive (+)

(Lab 8) Rate

The speed with which the reaction occurs and is determined by measuring how fast a reaction is consumed or a product is formed

(Lab 8) Rate Law

Relates the rate to the concentrations of reactants (rate = k [A]^x [B]^y

(Lab 8) Rate Constant

"k" varies with temperature and the reaction environment

(Lab 8) Zero Order

Change of initial concentration of a particular reactant results in no change in the reaction rate

(Lab 8) First Order

If a change in the initial concentration of a particular reactant results in a reaction rate change proportional to the concentration change

(Lab 8) Second Order

Doubling its concentration increases the rate factor of 2^2 = 4, triping its concentration causes the rate to increase by a factor of 3^2 = 9, etc

(Lab 8) Overall Reaction Order

Sum of the reaction orders, or the sum of the exponents in the rate law

(Lab 8) Method of Initial Rates

The amount of time required for fixed amounts of the reactants to react will be measured

(Lab 8) Clock Reaction

A side reaction, used as indication

(Lab 12) Oxidation-reduction reaction

Magnesium Metal, Mg, is oxidized to the magnesium cation, Mg 2+ by losing two electrons and the hydrogen ion, H+, is reduced to hydrogen gas, H2 by each hydrogen ion gained one electron

(Lab 12) Reducing agent

Magnesium - Chemical species being oxidized

(Lab 12) Oxidizing agent

Hydrogen ion - The chemical species undergoing reduction

(Lab 12) Oxidation state of Mg

zero, because magnesium is in its standard state whereas the magnesium in the cation

(Lab 4) Blank

Filling an empty cuvet with deionized water