chemistry lovers

BASICS STOICHIOMETRY One important aspect of the chemical reaction is a quantitative relationship between the substances involved in chemical reactions, both as reagent and as a result of the reaction. Stoichiometry (stoi-kee-ah-meth-tree) is a field of chemistry which involves the quantitative relationship between the substances involved in chemical reactions, both as reagent and as a result of the reaction. Stoichiometry is also related to the atomic ratio between the elements in a chemical formula, such as the atomic ratio of H and O atoms in the molecule H2O. The word stoichiometry derives from the Greek meaning of stoicheon element and metron meaning measure. An expert on French Chemistry, Jeremias Benjamin Richter (1762-1807) was the man who first laid the basic principles of stoichiometry. According to the stoichiometry is the science of measurement or comparison of quantitative measurements of the comparison between the chemical elements with each other Why do we have to study the stoichiometry? For one thing, because the study of chemistry can not be separated from doing experiments in the laboratory. Sometimes we have to react in the laboratory a number of grams of substance A to produce a number of grams of substance B. The question that often arises is if we have a number of grams of substance A, substance B gramkah how that will be generated? To answer that question we need stoichiometry. Stoichiometry is closely related to chemical calculations. To solve the problems of chemical calculations used the principles of stoichiometry which include chemical equations and the concept of the mole. In this lesson we will learn in advance about the principles of stoichiometry, then after that we will study the application of stoichiometry on chemical calculations along with example problems and how to solve them. 1.1 The concept of Mol Avogadro's number 2 atoms H atoms + 1 O -> 1 molecule H2O 1 dozen = 12 pieces 1 mol = 6, 022 x 10 particles 1.2 Measurement of Atom-Atom Mol In a chemical reaction, the atoms or molecules will be joined in the comparison figures are rounded. It has been explained that one mole consists of 6.022 x 1023 particles. This figure is not chosen arbitrarily, but rather represents the number of atoms in a sample of each element having a mass in grams equals the mass number atomic number elements, such as the atomic mass of 12.011 karbonadalah, then 1mol carbon atom has a mass of 12.011 g. Likewise, the atomic mass of oxygen is 15.9994, so 1 mole of oxygen atoms has a mass of 15.9994 g 1 mol C = 12.011 g C 1 mol O = 15.9994 g O So that becomes a tool keseimbanganlah us to measure the mole. To get one mole of each element, which we need to do is look at the mass of atoms of that element. Figures obtained is the number of grams of the element that we must take to get 1 mole of that element. 1.3 Measurement of Compound Mol As in the element, indirectly above equation can also be used to calculate the moles of the compound. The easiest path is to add all the mass of atoms that exist in the element. When a substance consisting of molecules (eg CO2, H2O or NH3), then the sum of the atomic masses are called mass or molecular weight molecules. In the chapters to come, will be found bnyak molecule compounds that do not contain clear. We will find that when an atom to react, often he will receive or lose negatively charged particles called electrons. Sodium and chlorine will react to this. When sodium chloride, NaC1, formed from its elements, each Na atom loses one electron, while each chlorine atom to gain electrons. At first element of the charged atoms of Na and C1 electrically neutral, but at the time of formation of NaC1, these atoms will get a charge. It will be written as Na (Na loses one positive because the negative electron charge) and C1 (C1 gets a negative because the electrons). Atom or collection of an iron atom that gets an electric charge are called ions. Kerana NaC1 solid composed of Na and C1, is said to be ionic compounds. The whole topic will be discussed further in subsequent chapters. For now just need diketahuai that the compounds do not contain molecular ions. The formula simply states the comparison of the various atoms in the compound. In NaC1, comparison ataomnya is 1:1. In compound CaC1, comparison of Ca and C1 atoms is 1:2 (take it easy, now you are not required to know that it is a compound CaC1 ions). Instead of using the term molecular NaC1 or CaC1, it is better to use the term formula unit to distinguish the two ions in NaC1 (Na and C1) or three ions in CaC1. For ionic compounds, the atomic mass number of the elements that exist in the formula known as the mass formula atauBerat Formulas. for NaC1 is from 22.99 to 35.44 = 58.44. one mole of NaC1 (6.022 x 10 units of the formula of NaC1) containing 58.44 g of NaC1. of course not use the term formula mass for ionic compound only. Can also be used for molecular compounds, in which case the term massaformila and molecular mass have the same meaning 1.4 Percent Composition A simple way of counting, but very useful and frequently used is the calculation of percent composition of a compound that is a percentage of the total mass (also called weight percent) provided by each element. 1.5 Empirical and Molecular Formulas The figures stated in the empirical formula of comparison atoms in a compound, such as CH 2 atomic ratio C: H is 1:2 and the like have been studied together with the mole ratio of atoms. To calculate the empirical formula, we must know the mass of each element in a given compound.