Chem 111

Accuracy

how close a measured value is to the true value

Precision

how close a set of measured values are to each other

Resolution

is the smallest distinguishable change that can be measured accurately

Significant Figures

the number of meaningful digits in a measured or calculated quantity. (limited by the measuring device)

Random Error

occurs due to chance and includes fluctuations in measurements. (can be evaluated by making multiple measurements)

Systematic Error

caused by the measuring device itself and is consistently either above or below the true value (scale calibration is off, minimized by using the same scale)

Human error

means a mistake was made in the experiment (not acceptable form of scientific error)

Beer's Law

states that if monochromatic radiation is allowed to fall on a solution, then the amount of light absorbed or transmitted is an exponential function of the concentration of the absorbing substance and of the length of the path of light through the sample (dumbed down terms: the more concentrated the solution and the longer light path travels through it, more light will be absorbed.

Transmittance

T

Path length

b

Absorbance

where A, the absorbance of the solution is defined as A=-log T

Colorimetry

one of the earliest and most useful applications of light absorption phenomena was in a technique of chemical analysis called . In _ a set of solutions of known concentrations of some light-absorbing substance-for example, food dye-is placed in a series of containers.

Spectrophotometers

the amount of light absorbed or transmitted is accurately and quantitatively detected and measured by solid state electronic devices.

"blank" medium

one which contains all but the absorbing solute ( will still lose intensity due to reflection)

𝜆max or wavelength of maximum absorbance

change in absorbance per unit change in concentration is greatest (absorption value is greatest)

calibration standards

standards must cover a reasonable concentration range over which a linear plot of absorbance vs. concentration is obtained

calibration graphs

absorbance vs. concentration for your assigned food dye. (not really sure what the definition should be for here know if it falls outside the standard calibration range the sample has to be redone, determines concentration for an unknown sample)

solution

homogeneous mixture composed of only one phase

solute

substance present in smaller amount

Concentration

tells us how much solute (in our case how much food dye) is present in a certain amount of solution

Dilution

the process of preparing a less concentrated solution from a more concentrated one by adding solvent.

stock solution

a concentrated solution used to prepare diluted solutions

Electromagnetic radiation

energy that can be described as existing in small "packets" (photons) or in terms of waves depending on the way it is observed

Spectroscopy

is the study of the interaction of electromagnetic radiation (ER) with matter

white light

If a particular sample contains all wavelengths of visible light, we label this , because it does not have any discernible color.

Absorption

atom absorbs energy, the electron can move to a higher energy level referred to as the excited state

Emission

if an atom has an electron in an excited state, when it returns to ground state energy is released.

Chromatography

separation technique that uses two phases of different polarity to separate components of a mixture

polarity

A lack of electrical symmetry in a molecule. Charge differences on opposite ends of a structure.

mobile phase

is a fluid that is able to flow though the porous stationary phase

stationary phase

the fixed, non-moving component against which the sample mixture is separated

dissolution

solvent must first dissolve the substances that are eventually going to react. this process involves the breaking of bonds and the formation of new associations.

solubility

defined as the concentration of solute in a saturated solution at a specified temperature

a polar covalent molecule

a water molecule is _, thus making it a good solvent for many polar and ionic compounds.

hydrogen bonds

In liquid water (and ice), the water molecules are fairly close together and attract each other, forming weak bonds called _. (bonds made by water).

nonpolar substances

do not dissolve in water because the long nonpolar hydrocarbon chains disrupt the hydrogen bonding between water molecules. (like dissolves like)

dissociation

process where a solute breaks apart into smaller components

electrolytes

The presence of charged ions in solution will allow the solution to conduct electricity, and these substances are called __.

non-electrolytes

e there are no charged components in solution, the solution does not conduct electricity and these solutes are called _.

acids

Compounds that react with water to produce H+ (aq) ions

acidic cation

a positively charged ion that produces H+ ions when it reacts with water (aluminium ion)

neutral cation

does not react with water (ex. sodium ion)

basic anion

negatively charged ion that produces OH- when it reacts with water (ex. carbonate)

convection

mass transport by moving fluids. E.g., a current within a liquid carrying dissolved substances with it.

diffusion

the spontaneous decrease in concentration differences due to random molecular motion

precipitation reaction

a reaction that produces a new compound that is not soluble in an aqueous solution

acid-base reaction/neutralization

characterized by the formation of covalent, neutral water molecules from hydrated hydrogen ions (H3O + ) and hydroxide ions (OH- ).

Complexation reactions

closely related to acid-base reactions. a reaction in which one or more coordinate-covalent bonds are produced during the formation of product.

complex

may be defined as a chemical compound in which there is one or more coordinate-covalent bonds.

coordinate-covalent bond

a covalent bond in which the shared pair of electrons is provided by the ligand.

ligands

electron rich species

Redox reactions

defined as chemical reactions in which electrons are transferred from one species to another.

Oxidation

loss of electrons

Reduction

gain of electrons

full ionic equation

writing a chemical equation in which the component ions of dissolved ionic compounds are written as separate ions—e.g., K+ and I - rather than KI.

spectator ions

ions that do not participate in a reaction

Net ionic equation

Reactions that involve spectator ions can also be written in a form in which the spectator ions are deleted (do not appear).

molecular equation

a reaction equation that shows the complete chemical formulas of all reactants and products

qualitative analysis

involves finding out what elements or substances are present in the sample

quantitative analysis

involves the determination of how much of each component is in the sample

melting point analysis

One way chemists qualitatively assess the purity of a product.

reaction yield

how much product was produced, to determine the efficiency of the reaction.

theoretical yield

maximum amount of product that can be theoretically obtained from a reaction of a given amount of the limiting reagent

limiting reagent

is the reactant present in the smallest stoichiometric quantity in a mixture of reactants and the amount of product that can form is limited by the complete consumption of the ___.

percent yield

determine the efficiency of the reaction. ratio of the experimental yield (the actual amount of product isolated in the experiment) to the theoretical yield.

Arrhenius acid

is anything that produces a hydrogen ion (H+ ) when added to water. H+ ions are referred to simply as a protons.

Arrhenius base

is anything that produces a hydroxide ion (OH- ) when added to water.

Brønsted-Lowry bases

"proton acceptors"

BrønstedLowry acids

"proton donors"

Lewis acid

defined as an "electron pair acceptor"

Lewis base

"electron pair donor"

acid-base indicator

is a substance that changes colors at different pH values.

hygroscopic

means that the solid attracts water from the atmosphere. (rapidly absorbs water from the air)

standardization

method by which a solution of unknown concentration is determined by comparison to a solution with a known concentration

titration

technique used to determine the concentration of an unknown solution through the slow addition of a solution of known concentration.

equivalence point

the acid is completely reacted with the base.

back titration

Method where an excess of a reagent is reacted with a sample. The unreacted reagent is then determined by titration.

calorie

as the amount of energy required to raise the temperature of 1.00 g of water by 1.00 °C from a standard temperature at one atmosphere pressure.

Food Calories

describe an amount of energy. represent an amount of energy equal to 1000 scientific calories.

calorimetry

The precise measurement of heat flow out of a system for chemical and physical processes (we carry out a reaction in such a way that it will change the temperature of its surroundings. Then, we measure the temperature change in the surroundings to determine how much energy was released or absorbed)

calorimeter

Any device that allows you to measure the change in temperature due to a chemical reaction

specific heat

_ of a substance is defined as the amount of energy required to raise the temperature of 1.00 gram of a substance by 1.00 °C.