General Chemistry

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry Glassware is a regular appearance in the professional chemistry laboratory, because it has a relatively low cost, extreme durability, and specific levels of precision. While some labware is being supplemented with plastic or even everyday kitchen materials, glass is still the standard material by which laboratory work is done. While there are few rules about glassware, there are some best practices for...

Source: Laboratory of Dr. Michael Evans — Georgia Institute of Technology A solution is a homogeneous mixture containing some components in small amounts, called solutes, and one component in a large amount, called the solvent. Solid-liquid solutions contain one or more solid solutes dissolved in a liquid solvent. Solutions are ubiquitous in chemistry: they are used to store and handle small amounts of material, carry out chemical reactions, and develop materials with controllable properties.

Source: Laboratory of Dr. Michael Evans — Georgia Institute of Technology The ratio of the mass of a substance to its volume is known as the mass density or, simply, the density of the substance. Density is expressed in units of mass per volume, such as g/mL or kg/m3. Because the density of a substance does not depend on the amount of substance present, density is an “intensive property”. To measure the density of a sample of material, both the mass and volume of the sample must be determined.

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry Determining the composition of a solution is an important analytical and forensic technique. When solutions are made with water, they are referred to as being aqueous, or containing water. The primary component of a solution is referred to as the solvent, and the dissolved minor component is called the solute. The solute is dissolved in the solvent to make a solution. Water is the most common solvent in...

Source: Laboratory of Dr. Neal Abrams - SUNY College of Environmental Science and Forestry Determining the chemical formula of a compound is at the heart of what chemists do in the laboratory every day. Many tools are available to aid in this determination, but one of the simplest (and most accurate) is the determination of the empirical formula. Why is this useful? Because of the law of conservation of mass, any reaction can be followed gravimetrically, or by change in mass. The empirical...

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry An ionic compound's solubility can be determined via qualitative analysis. Qualitative analysis is a branch of analytical chemistry that uses chemical properties and reactions to identify the cation or anion present in a chemical compound. While the chemical reactions rely on known solubility rules, those same rules can be determined by identifying the products that form. Qualitative analysis is not...

Source: Laboratory of Dr. Zhongqi He - United States Department of Agriculture Acids and bases are substances capable of donating protons (H+) and hydroxide ions (OH-), respectively. They are two extremes that describe chemicals. Mixing acids and bases can cancel out or neutralize their extreme effects. A substance that is neither acidic nor basic is neutral. The values of proton concentration ([H+]) for most solutions are inconveniently small and difficult to compare so that a more practical...

Source: Laboratory of Dr. Yee Nee Tan — Agency for Science, Technology, and Research Titration is a common technique used to quantitatively determine the unknown concentration of an identified analyte.1-4 It is also called volumetric analysis, as the measurement of volumes is critical in titration. There are many types of titrations based on the types of reactions they exploit. The most common types are acid-base titrations and redox titrations.5-11 In a typical titration process, a standard...

Source: Laboratory of Dr. Andreas Züttel - Swiss Federal Laboratories for Materials Science and Technology The ideal gas law describes the behavior of most common gases at near-ambient conditions and the tendency of all chemical matter in the dilute limit. It is a fundamental relationship between three measurable macroscopic system variables (pressure, temperature, and volume) and the number of molecules of gas in the system, and is therefore an essential link between the microscopic and the...

Source: Laboratory of Dr. Michael Evans — Georgia Institute of Technology The equilibrium constant, K, for a chemical system is the ratio of product concentrations to reactant concentrations at equilibrium, each raised to the power of their respective stoichiometric coefficients. Measurement of K involves determination of these concentrations for systems in chemical equilibrium. Reaction systems containing a single colored component can be studied spectrophotometrically. The relation between...

Source: Laboratory of Dr. Lynne O'Connell — Boston College When the conditions of a system at equilibrium are altered, the system responds in such a way as to maintain the equilibrium. In 1888, Henri-Lewis Le Châtelier described this phenomenon in a principle that states, "When a change in temperature, pressure, or concentration disturbs a system in chemical equilibrium, the change will be counteracted by an alteration in the equilibrium composition." This experiment demonstrates Le Châtelier's...

Source: Laboratory of Lynne O' Connell — Boston College When a solid compound is dissolved in a solvent, the freezing point of the resulting solution is lower than that of the pure solvent. This phenomenon is known as freezing-point depression, and the change in temperature is directly related to the molecular weight of the solute. This experiment is designed to find the identity of an unknown compound by using the phenomenon of freezing-point depression to determine its molecular weight. The...

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry All chemical reactions have a specific rate defining the progress of reactants going to products. This rate can be influenced by temperature, concentration, and the physical properties of the reactants. The rate also includes the intermediates and transition states that are formed but are neither the reactant nor the product. The rate law defines the role of each reactant in a reaction and can be used to...

Source: Laboratory of Dr. Terry Tritt — Clemson University Differential Scanning Calorimetry (DSC) is a method of thermodynamic analysis based on heat-flux method, wherein a sample material (enclosed in a pan) and an empty reference pan are subjected to identical temperature conditions. The energy difference that is required to maintain both the pans at the same temperature, owing to the difference in the heat capacities of the sample and the reference pan, is recorded as a function of...

Source: Laboratory of Dr. Neal Abrams — SUNY College of Environmental Science and Forestry Transition metals are found everywhere from vitamin supplements to electroplating baths. Transition metals also make up the pigments in many paints and compose all minerals. Typically, transition metals are found in the cationic form since they readily oxidize, or lose electrons, and are surrounded by electron donors called ligands. These ligands do not form ionic or covalent bonds with the metal center,...