chemistry

Biological Chemistry - Food Chemistry Home > Biological Chemistry > Food Chemistry FOOD CHEMISTRY Caramelization in Cooking - Caramelization Reactions Food Chemistry: Antioxidants and Oxidation Reactions in Foods Food Chemistry: The browning reaction or reactions of amino acids during cooking     Food Preservatives: Sulfites and SO2               Food chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods. It deals with the production, processing, distribution, preparation, evaluation, and utilization of food. Basic food chemistry is mainly concerned with the three primary components in food: carbohydrates , lipids and proteins . Carbohydrates – empirical formula C x (H 2 O) z - are t...

Analytical Chemistry - Calibration Home > Analytical Chemistry > Calibration CALIBRATION What is calibration? Calibrated instruments|Analytical Chemistry Calibrating a pH meter using buffers Quantitative Analysis by Atomic Absorption Performance Verification of Analytical Balances according to ISO/IEC 17025 Calibration and Outliers - Statistical Analysis Calibration of an instrument in Analytical Chemistry is the operation that determines the functional relationship between measured values (signal intensities S at certain signal positions zi) and analytical quantities characterizing types of analytes qi and their amount ( content , concentration ) n. Calibration includes the selection of the model (its functional form), the estimation of the model parameters as well as the errors, and their validation. During calibration , the in...

Atomic Absorption Home > Analytical Chemistry > Atomic Absorption ATOMIC ABSORPTION Atomic Absorption Spectrometry (AAS) Sampling Techniques for Atomic Absorption Spectrometry Light sources for atomic absorption     Quantitative Analysis by Atomic Absorption       Advantages and Disadvantages of Atomic Absorption Spectrometry and Graphite Furnace       Atomic absorption spectrometry (AAS) is an analytical technique that measures the concentration of an element by measuring the amount of light (intensity of light) that is absorbed - at a characteristic wavelength - when it passes through a cloud of atoms of this element. As the number of atoms in the light path increases, the amount of light absorbed increases in a predictable way. Modern atomic absorption spectrometry was introduced in 1955 as ...

Acid & Base Equilibria Home > Analytical Chemistry > Acid & Base Equilibria ACID & BASE EQUILIBRIA - STRONG ACIDS & BASES Ionic equilibrium - A general expression of the pH of a strong acid Strong acids and bases - Weak acid and bases - Dissociation constants and pK's pH of a strong acid – Examples     Strong Acids & Bases: pH Calculations involving mixtures of strong acids and bases       Chemical Equilibrium Calculations in Analytical Chemistry   Self-ionization of water - Autoionization of water - The ion product of water (kw)   ACID & BASE EQUILIBRIA - WEAK ACIDS & BASES Weak Acids and Bases – Calculate the pH of a weak acid (a general equation Solving Weak Acid and Weak Base pH problems Weak Acid Weak Base pH calculation solved example ...

How to determine the order of a reaction? Determining the form of the Rate Law (Order of Reaction) by the method of Initial Rates Home > Rate of a Chemical Reaction - Chemical Kinetics > Rates of Chemical Reactions and the Collision Model > How to determine the order of a reaction by the initial rates method?   How to determine the order of a reaction by the initial rates method?   A rate law is an expression which shows how the rate of a reaction depends on the concentrations of reactants. For the decomposition of NO 2 we can write: 2NO 2 (g) → 2NO(g) + O 2 (g)  Rate = k [NO 2 ] n      (Rate Law) k is the rate constant and n is the order of reaction (n can be positive or negative, integer or fraction) Both k and n must be determined experimentally. For the general reaction: aA + bB → cC + dD   (1) the rate law is given by:   Rate = k. [A] m [B] n     (2)   There are two types of rate laws: The differential rat...

rates of chemical reactions and the collision model Home > Rate of a Chemical Reaction - Chemical Kinetics > Rates of Chemical Reactions and the Collision Model   Rates of Chemical Reactions and the Collision Model   Reaction rates are affected both by reactant concentrations and by temperature . The collision model , that is based on the kinetic-molecular theory , explains for both of these effects at the molecular level. In general only a small number of reactant collisions leads to products (in certain cases 1 in 10 13 collisions). The basic principles of the collision model (collision theory) are as follows: Molecules must collide to react – Collisions are necessary to transfer kinetic energy, to break reactant chemical bonds and form product bonds The greater the number of collisions per second the greater the reaction rate – This agrees with the observation that as reactant concentration increases the rate of a reaction...

Rate of a Chemical Reaction Home > Rate of a Chemical Reaction - Chemical Kinetics   Rate of a Chemical Reaction - Chemical Kinetics Chemical kinetics is the area of chemistry in which reaction rates are studied. Kinetics is largely an experimental science. Reaction rate is called the speed at which a chemical reaction occurs. Some chemical reactions are complete within a fraction of a second (explosions) while others take years (corrosion of metals) or even centuries (formation of mineral’s in Earth). The basic concepts covered in this post are the following: Factors that affect the rate of chemical reactions Definition of the rate of reaction   What are the factors that affect the rate of chemical reactions? Four factors allows us to change the rate at which a reaction occurs:   Physical state and nature of the reactants Reactants in the same physical state tend to react faster since there is a greate...