Gen Chem Lab 1

Absorbance (A)

A measure of the amount of light absorbed by a sample at a specific wavelength. Directly proportional to concentration and pathlength according to Beer's Law.

Accuracy

How close a measurement or result is to the true or accepted value. Quantified by percent error.

Analyte

The substance whose concentration or amount is being determined in an analysis.

Analytical Balance

A type of balance used for weighing small masses with high precision (typically to the nearest 0.0001 g).

Antacid Tablet

A tablet containing basic compounds (like CaCO3) used to neutralize excess stomach acid.

Back Titration

A titration method where an excess of a reagent is added to the analyte, and the excess reagent is then titrated with a second substance. Used when the analyte reacts slowly or is insoluble.

Beer's Law

A law stating that the absorbance of a solution is directly proportional to the concentration of the absorbing substance and the pathlength of the light through the solution (A = εbc).

Buret

A graduated glass tube with a stopcock at one end, used to accurately dispense variable volumes of liquid, especially in titrations.

Calorimeter

A device used to measure the heat absorbed or released during a chemical or physical process.

Calorimetry

The study of heat flow.

Centrifugation

A process that uses centrifugal force to separate components of a mixture based on density. In the lab, used to separate precipitates from solutions.

Complex Ion

An ion consisting of a central metal atom or ion bonded to one or more ligands.

Concentration

The amount of solute present in a given amount of solution. Can be expressed in various units, such as molarity or percent by mass.

Correlation Coefficient (R)

A statistical measure that indicates the strength and direction of a linear relationship between two variables. R-squared is R multiplied by itself and indicates the proportion of the variance in the dependent variable that is predictable from the independent variable.

Covalent Compound

A compound formed by the sharing of electrons between atoms, typically nonmetals.

Cuvette

A small transparent container used to hold liquid samples for spectroscopic measurements, such as absorbance in Beer's Law experiments.

Decantation

A process of carefully pouring off a liquid from a solid or another liquid that has settled, leaving the solid behind.

Density (ρ)

An intensive physical property defined as mass per unit volume (ρ = m/V).

Dilution

The process of reducing the concentration of a solute in a solution by adding more solvent.

Dipole Moment

A measure of the polarity of a molecule, resulting from the unequal distribution of electron density.

Dissolution

The process by which a solute dissolves in a solvent to form a solution.

Electron Geometry Arrangement (EGA)

The spatial arrangement of all electron groups (bonding pairs and lone pairs) around a central atom.

Endothermic Reaction

A reaction that absorbs heat from the surroundings, causing the temperature of the surroundings to decrease.

Endpoint

The point in a titration where the indicator changes color, signaling the completion of the reaction.

Equivalence Point

The point in a titration where the stoichiometric amount of titrant has been added to react completely with the analyte.

Exothermic Reaction

A reaction that releases heat to the surroundings, causing the temperature of the surroundings to increase.

Filtration

A process used to separate solid particles from a liquid or gas by passing the mixture through a filter medium.

Formal Charge

A calculated charge assigned to an atom in a molecule or ion, assuming that electrons in a chemical bond are shared equally between atoms. Used to evaluate the most likely Lewis structure.

Graduated Cylinder

A cylindrical glass vessel with markings along its side, used for measuring approximate volumes of liquids. Less precise than a volumetric pipet.

Indicator

A substance that changes color in response to a specific chemical condition, such as pH in acid-base titrations, used to signal the endpoint of a reaction.

Intensive Property

A physical property that does not depend on the amount of substance present, such as density and temperature.

Ionic Compound

A compound formed by the electrostatic attraction between oppositely charged ions, typically a metal and a nonmetal.

Ligands

Molecules or ions that bind to a central metal atom or ion to form a complex ion.

Limiting Reactant

The reactant that is completely consumed in a chemical reaction, thereby limiting the amount of product that can be formed.

Lewis Structure

A diagram that shows the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule.

Mean (Average)

The sum of a set of values divided by the number of values in the set.

Molar Absorptivity (ε)

A constant that describes how strongly a substance absorbs light at a specific wavelength; a measure of the substance's ability to absorb light.

Molar Enthalpy of Dissolution (ΔHsoln)

The heat absorbed or released when one mole of a substance dissolves in a solvent at constant pressure.

Molarity (M)

A unit of concentration defined as the number of moles of solute per liter of solution (mol/L).

Molecular Shape

The three-dimensional arrangement of the atoms in a molecule, determined by the arrangement of electron groups around the central atom and considering only the positions of the atoms.

Nomenclature

A system for naming chemical compounds.

Octet Rule

The tendency of atoms to gain, lose, or share electrons to achieve a stable electron configuration with eight valence electrons.

Oxidation Number (O.N.)

A number assigned to an atom in a molecule or ion that indicates the degree of oxidation (loss of electrons) or reduction (gain of electrons) of that atom compared to its elemental state.

Oxoacid

An acid containing hydrogen, oxygen, and another nonmetal.

Pathlength (b)

The distance that light travels through a sample in a spectroscopic measurement, typically the width of the cuvette.

Percent by Mass (% by mass)

A unit of concentration defined as the mass of the solute divided by the mass of the solution, multiplied by 100%.

Percent Error

A measure of the accuracy of an experimental result, calculated as the absolute difference between the experimental value and the true value, divided by the true value, multiplied by 100%.

Pipet Pump

A device used to draw liquid into a pipet and dispense it, providing better control than mouth pipetting.

Precision

How close repeated measurements of the same quantity are to each other; a measure of the reproducibility of a measurement. Quantified by standard deviation.

Precipitate (ppt)

A solid that forms from a solution during a chemical reaction.

Qualitative Analysis

A set of analytical methods used to identify the components present in a sample ("What is in a sample?").