Virtual Chemistry Experiments Web Pages
Isosurfaces of various atomic orbitals are displayed to show the orbital shapes.
Electron density maps, isosurfaces and graphs of wavefunctions and radial distribution functions are explained and used to illustrate the shapes and characteristics of atomic orbitals.
Shell and subshell designations are explained. Radial distribution functions and isosurfaces are used to show how orbital size depends upon the principal and angular momentum quantum numbers.
The technique of calorimetry and the properties of heat capacity and specific heat capacity are explained. The experiments determine the heat capacity of the calorimeter and the heat capacity of copper.
A chemical reaction is a source of heat transfer in this calorimetry experiment. The molar enthalpy of solution for ammonium nitrate is determined.
The neutralization reaction is explained and the molar enthalpy of neutralization is determined. There are two reactants in the neutralization reaction; thus the limiting reactant must be identified in order to determine the molar enthalpy of neutralization.
Strategies are discussed for studying systems in which two chemical reactions occur simultaneously. In this experiment, calcium hydroxide is dissolved in a hydrochloric acid solution. The molar enthalpy of reaction is determine, and Hess's Law is used to calculate the molar enthalpy of solution of calcium hydroxide.
The combustion reaction is explained, and the molar enthalpy of combustion for methane is determined by bomb calorimetry. The molar enthalpy of combustion is then used to calculate the molar enthalpy of formation of methane. The Ideal Gas Law is used to calculate the amount of methane in the bomb. The calorimeter is no longer portrayed as a perfectly insulated system. Instead a graphical analysis the temperature-time data is used to account for heat transfer with the surroundings.
The equilibrium state is described in terms of the rate of the forward and reverse reactions. The equilibrium constants KP and KC and the Law of Mass Action are introduced.
The equilibrium constant and its significance are discussed. The equilibrium constants for two reactions with a single gas-phase product are measured.
The use of a reaction table (ICE Table) to manage equilibrium calculations is described. The equilibrium constants for two reactions are measured.
Le Châtelier's Principle is introduced. The distinction between initial amounts and equilibrium amounts of material is explained. The equilibrium amounts of carbon, water, carbon monoxide, and hydrogen for the steam reforming reaction are measured as the initial amounts of the various species are changed. The effect of temperature and system volume is also explored.
The stopped-flow technique and its use in studying chemical reactions is described. The speed or rate of a reaction is explained. Concentration vs time plots are recorded for reactants and product in a chemical reaction.
Differential rate laws for zero-, first-, and second-order reactions are explained. The differential rate law and the rate constant are determined for a reaction by examining how the rate of reaction varies with the reactant concentration.
Integrated rate laws for zero-, first-, and second-order reactions are explained and illustrated. The rate law and the rate constant are determined for a reaction by preparing characteristic kinetics plots from concentration-time data.
The determination of a rate law by the Method of Initial Rates is explained. The rate law and rate constant for a reaction is determined using the Method of Initial Rates.
The determination of a rate law by the Isolation Method is described. The rate law and rate constant for a reaction is determined using the Isolation Method.
Same as the Isolation Method but with experimental data preloaded.
The weight percents of carbon and hydrogen in an unknown compound are determined in a virtual experiment. This information is used to determine the empirical formula.
The physical meaning of pressure and operation of a U-tube manometer are explained. Experiments involve reading a manometer, measuring pressure when the manometer contains a liquid other than water, compensating for the vapor pressure of a volatile liquid in the manometer.
Boyle's experiments involving pressure and volume are discussed. Boyle's historical experiments are repeated to formulate the relationship between the pressure and volume of a gas.
Same as the Boyle's Law web page but with experimental data preloaded.
Boyle's law is used to predict how changing the volume of a gas will change its pressure.
Charles's and Gay-Lussac's experiments involving temperature and volume are discussed and performed. An estimate for absolute zero is determined.
Same as the Charles's Law web page but with experimental data preloaded.
The density, molar concentration, and molar volume of a gas are measured to illustrate Avogadro's Law.
The Ideal Gas Law is explained and tested by measuring the pressure of a gas at various molar concentrations. The value of the gas constant is determined graphically.
The partial pressure of a gas is defined. Two gases are allowed to mix and the final pressure of the gas mixture is measured.
The origin and significance of hybrid orbitals is explained and illustrated with energy diagrams, radial distribution functions and electron density plots.
Small spheres are arranged in a linear, trigonal planar, or tetrahedral geometry around a central atom. Various hybrid orbitals may be displayed for the central atom. Only the proper hybridization scheme will provide a set of orbitals that are directed at the spheres.
Kinetic Molecular Theory
The postulates of the Kinetic Molecular Theory are presented and discussed. A molecular dynamics simulation of a gas is used to illustrate the concepts.
Alternate explanation of the principles of the Kinetic Molecular Theory, with a discussion of similarities and differences between the Kinetic Molecular Theory and principles of Molecular Dynamics Simulations.
The Maxwell Distribution is introduced and a molecular dynamics simulation is employed to explore the effect of temperature on the shape of the Maxwell Distribution.
Alternate tutorial on the Maxwell Distribution.
Illustration of the physical origin of pressure using a molecular dynamics simulation.
Relation between pressure and volume (at constant temperature and amount of gas) is explored using molecular dynamics simulations.
A molecular dynamics simulations is used to illustrate random-walk motion and chemical diffusion.
Principles and implementation of the Valence-Shell Electron-Pair Repulsion Model are explained. Examples of the basic geometries are shown.
Test your ability to predict the shapes of molecules.
Three concepts are presented for consideration when applying the VSEPR Model. Molecules with geometries that do not conform with the ideal VSEPR Model bond angles are discussed.
Nuclear spin and Larmor precession are explained. An animation illustrates the precession of the nuclear magnetic moment.
The bulk magnetization is explained and its precession illustrated by an animation.
Trigonometric functions are used to compare the real and rotating frames of reference. In the simulation, the chemical shift is determined from measurements in the rotating frame.
The kinetics of the relaxation of the bulk magnetization to its equilibrium value is described. The dependence of the free induction decay on precession frequency, T1, and T2 are explored in the simulation.
The use of radiofrequency pulses to manipulate the bulk magnetization is described. The simulation steps through the stages of the basic NMR experiment.
The use of the Fast Fourier Transform to convert the FID to a spectrum is described.
The simulation depicts a spin system with multiple types of nuclei, giving rise to multiple peaks in the NMR spectrum. The peaks are integrated to reveal the relative number of each type of nucleus.
The phase of an NMR spectrum and application of the phase correction is explained. The simulation produces an out-of-phase spectrum, which must be phase corrected.
The inversion recovery experiment is explained. The simulation steps through the stages of the inversion recovery experiment. The value of the spin-lattice relaxation time is measured.
The spin-echo experiment is explained. The simulation steps through the stages of the spin-echo experiment. The value of the spin-spin relaxation time is measured.
A heating curve is recorded for a substance and the accompanying phase changes are depicted. The viewer is asked to determine the melting point, boiling point, enthalpy of fusion, enthalpy of vaporization, and heat capacities for the solid, liquid and gas.
A solid-liquid-gas phase diagram is presented. A cylinder containing the pure substance is displayed. Users change the temperature and pressure of the substance while comparing the position on the phase diagram with the phases present in the cylinder.
The vapor pressure of ethanol is measured at various temperatures. A Classius-Clapeyron plot is prepared, and the viewer is asked to determine the normal boiling point, enthalpy of vaporization, and entropy of vaporization for ethanol.
Same as the Vapor Pressure web page but with experimental data preloaded.
Basic principles of spectrophotometry are illustrated. Transmittance and absorbance are calculated from experimental data.
The effects of the sample concentration and cell pathlength on transmittance and absorbance are explored.
The significance of the molar absorptivity is discussed. Experimental measurements are used to determine the molar absorptivity of a dye.
The absorbance spectrum is explained, and points on a spectrum are measured.
The construction of a calibration curve and its use in chemical analysis is explained. A calibration curve is prepared and used to determine the concentration in an unknown solution.
Valence Bond Theory
The concept of a chemical bond is illustrated with electron density maps and isosurface for the dihydrogen molecule.
Isosurfaces of atomic orbitals as well as O-H σ orbitals and lone pair orbitals are used to illustrate bonding in the water molecule.
Isosurfaces of atomic orbitals as well as H-C and C-N σ orbitals, CN π orbitals, and the lone pair orbital are used to illustrate bonding in the hydrogen cyanide molecule.
Isosurfaces of atomic orbitals as well as H-C and C=O σ orbitals, the C=O π orbital, and the lone pair orbitals are used to illustrate bonding in the formaldehyde molecule.
Isosurfaces of atomic orbitals as well as C=O σ and π orbitals and lone pair orbitals are used to illustrate bonding in the carbon dioxide molecule.