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Acids and Bases - Properties and Reactions - Arrhenius, Brønsted-Lowry, and Lewis Definitions
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Acids and Bases - Definitions, Properties, and Reactions. There are three different definitions for an acid. The one that is most frequently used in introductory chemistry courses is named after the Swedish chemist Svante Arrhenius. Arrhenius acids are compounds that dissociate in water and yield hydrogen ions (H. Common compounds that fit this definition include hydrochloric acid. Ions Examples of Arrhenius bases are sodium hydroxide. Definitions - Brønsted-Lowry. Gives up a proton (H. Organic acids are...
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The Atom - The History of Atomism
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The Atom - The History of Atomism. Demcoritus was a citizen of Greece in the 4th and 5th century B.C. Although not well known in his day, he was known to Plato. His idea of an atomic model was never tested, nor it could it have been with the technology of his day. In the early 19th century, Englishman John Dalton revived the atomic model with a five part theory that would set the course in atomic discoveries for the next 130 years:. 1 Elements are made of extremely small particles called atoms. 4) Grimes...
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Bonding - Ionic, Covalent, Single, Double, Triple, Sigma, and Pi Bonds
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Bonding - Ionic, Covalent, Single, Double, Triple, Sigma, and Pi Bonds. What is a Bond? A chemical bond occurs when the sharing or transfer of electrons between two atoms results in them being attracted to one another. Since there is a great variation in the strength of attraction between the two atoms, and the causes for that attraction, bonds can be categorized accordingly. Otherwise, there will always be one element that wants electrons more than another. Electronegativity. Less than 1.65. The answer ...
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Calorimetry - The Study of Heat Transfer
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Calorimetry - The Study of Heat Transfer. Absolute zero is the temperature at which particles reach a minimum amount of energy, vibration, and motion. The kelvin scale is based on this temperature, and is 0 K. On the Celsius scale, absolute zero is -273.15°C. On the Fahreneheit scale, it is nearly -460°F. What is a Calorie? The calorie is a unit of measurement of heat. It is no longer used, as the SI. 1 calorie = 4.184 J. Represents heat, measured in joules. C. Use the specific heat. Is calculated by sub...
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Stoichiometry - Mass/Mass, Mass/Volume, Volume/Volume, Limiting Reactant/Reagent, Excess Reactant/Reagent, STP/Non-STP Conditions, Solutions, Titrations, Density, Enthalpy and Molarity - Stoichiometry Calculator
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Stoichiometry is a quantitatve process. Given an initial mass or volume of reactant or product, the molar relationships between reactants and products in a chemical reaction are used to calculate a specific mass or volume of another reactant or product. Essentially, all stoichiometry problems can be broken down into three steps:. 1 Take the given quantity (i.e. mass or volume) and convert to moles. 2 Use a mole to mole ratio to find the number of moles of the desired compound. Determine the mass of iron.
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Radioactivity - Alpha, Beta, and Gamma Radiation - Half-Lives and Decay
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What Does it Mean to be Radioactive? For introductory purposes, we can say that two criteria need to be met:. Bull; The nucleus is unstable - meaning it will spontaneously decay. Bull; There will be emission of energy and a change in mass and/or atomic number for that particle. You Cannot Escape Radioactivity. Half-Life Problems - How Much Remains? If a 100. g sample of thorium-230 is analyzed, how much is left after 3.2×10 5. As the subscript 0 indicates it represents initial mass. The variable A re...
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Thermochemistry - Enthalpy, Entropy, and Gibbs Free Energy - What Makes Reactions Work?
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Thermochemistry - Enthalpy, Entropy, and Gibbs Free Energy. The enthalpy of a reaction is a measure of how much heat is absorbed or given off when a chemical reaction takes place. It is represented by ΔH reaction. And is found by subtracting the enthalpy of the reactants from the enthalpy of the products:. Sigma;ΔH f products. Sigma;ΔH f reactants. Find sodium sulfide, or Na 2. The entropy change from a reaction, or S reaction. Is a measure of the dispersal of energy and matter that takes place during a ...
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Significant Digits/Significant Figures
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Here's a little story that may help you understand the idea behind significant digits:. Some tourists at the Museum of Natural History are marveling at the dinosaur bones. One of them asks the guard, "Can you tell me how old these bonds are? The guard replies, "They're three million, four years and six months old.". That's an awfully exact number," says the tourist. "How do you know their age so precisely? The answer is you canâ t! The number 147.240296 m 2. If there were a more precise meterstick than t...
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The Periodic Table of the Elements - Trends in Atomic Radius, Electronegativity, Ionization Energy, Density, and Specific Heat
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Physical and chemical properties as well as background information on all the elements. Each element includes links to other sites that feature that element. Trends - Atomic Radius. Smaller radii (top of groups/right of periods). Larger radii (bottom of groups/left of periods). The closer you get to. This is due to the absence, or at least weak, shielding effect shown by smaller elements. Trends - Ionization Energy. The "nth" ionization energy. Bull; atomic radius decreases. Thus, removing an electro...
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