# General Chemistry

## Give Your Students the Foundational Knowledge They Need

Our integrated solution helps students collect accurate data, visualize trends and relationships, and explore different hypotheses for both conventional and innovative experiments.

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## Example Data

Complete an acid-base titration with our pH probes that have 0.1 pH unit accuracy and a drop counter that accurately converts drops to volume.

Our affordable Go Direct® SpectroVis Plus Spectrophotometer allows you to record the full absorbance spectrum of copper (II) sulfate to find λmax to create a graph of Abs vs. concentration as instructed from the experiment “Determining the Concentration of a Solution: Beer’s Law.”

This is only the beginning of what’s possible. See the recommendations below to get started with general chemistry.

### Rate Determination and Activation Energy

An important part of the kinetic analysis of a chemical reaction is to determine the activation energy, Ea. Activation energy can be defined as the energy necessary to initiate an otherwise spontaneous chemical reaction so that it will continue to react without the need for additional energy. An example of activation energy is the combustion of paper. The reaction of cellulose and oxygen is spontaneous, but you need to initiate the combustion by adding activation energy from a lit match.

In this experiment you will investigate the reaction of crystal violet with sodium hydroxide. Crystal violet, in aqueous solution, is often used as an indicator in biochemical testing. The reaction of this organic molecule with sodium hydroxide can be simplified by abbreviating the chemical formula for crystal violet as CV.

${\text{C}}{{\text{V}}^{\text{ + }}}{\text{ }}{\text{(aq) + O}}{{\text{H}}^{\text{ - }}}{\text{ (aq)}} \to {\text{CVOH (aq)}}$

As the reaction proceeds, the violet-colored CV+ reactant will slowly change to a colorless product, following the typical behavior of an indicator. You will measure the color change with a Vernier Colorimeter or a Vernier Spectrometer. You can assume that absorbance is directly proportional to the concentration of crystal violet according to Beer’s law.

The molar concentration of the sodium hydroxide, NaOH, solution will be much greater than the concentration of crystal violet. This ensures that the reaction, which is first order with respect to crystal violet, will be first order overall (with respect to all reactants) throughout the experiment. You will monitor the reaction at different temperatures, while keeping the initial concentrations of the reactants the same for each trial. In this way, you will observe and measure the effect of temperature change on the rate of the reaction. From this information you will be able to calculate the activation energy, Ea, or the reaction.

### The Base Hydrolysis of Ethyl Acetate

The reaction of ethyl acetate and hydroxide ions yields ethanol and acetate ions

The progress of this reaction can be observed by monitoring the conductivity of the reaction mixture. Although the reactants and products each contain an ion, the OH ion has a higher ionic mobility than the CH3COO ion. This results in a net decrease in the conductivity of the reaction mixture as the reaction proceeds.

### Exploring the Properties of Gases

The purpose of this investigation is to conduct a series of experiments, each of which illustrates a different gas law. You will be given a list of equipment and materials and some general guidelines to help you get started with each experiment. Four properties of gases will be investigated: pressure, volume, temperature, and number of molecules. By assembling the equipment, conducting the appropriate tests, and analyzing your data and observations, you will be able to describe the gas laws, both qualitatively and mathematically.

The basic counting unit in chemistry, the mole, has a special name, Avogadro’s number, in honor of the Italian scientist Amadeo Avogadro (1776-1856). The commonly accepted definition of Avogadro’s number is the number of atoms in exactly 12 g of the isotope 12C, and the quantity itself is 6.02214199 × 1023.

A bit of information about Avogadro seems appropriate. His full name was Lorenzo Romano Amedeo Carlo Avogadro (almost a mole of letters in his name). He was a practicing lawyer until 1806 when he began his new career teaching physics and math at the University of Turin, where he was later promoted to the chair of physical chemistry. In 1811, Avogadro published a paper in the Journal de Physique, entitled “Essay on a Manner of Determining the Relative Masses of the Elementary Molecules of Bodies, and the Proportions in Which They Enter into These Compounds,” which pretty much says it all. This paper includes the statement that has come to be regarded as Avogadro’s Hypothesis:

The first hypothesis to present itself in this connection, and apparently even the only admissible one, is the supposition that the number of integral molecules in any gases is always the same for equal volumes, or always proportional to the volumes. Indeed, if we were to suppose that the number of molecules contained in a given volume were different for different gases, it would scarcely be possible to conceive that the law regulating the distance of molecules could give in all cases relations as simple as those which the facts just detailed compel us to acknowledge between the volumes and the number of molecules.

In this experiment, you will confirm Avogadro’s number by conducting an electrochemical process called electrolysis. In electrolysis, an external power supply is used to drive an otherwise nonspontaneous reaction. You will use a copper strip and a zinc strip as the electrodes, placed in a beaker of sulfuric acid. You will make the cell electrolytic by using the copper strip as the anode and the zinc strip as the cathode. By determining the average current used in the reaction, along with the knowledge that all of the copper ions formed are the 2+ cations, you will calculate the number of atoms in one mole of copper and compare this value with Avogadro’s number.

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