Mole concept

Gram molecule of any substance is considered as mole. Both gram molecule and gram atom can be represented by mole. The term mole of a substance may be defined as the weight in grams which contain 6.023 x 10 molecules. In the case of mono atomic molecule one mole represents the weight in grams of the element which contains 6.023 x 10 atoms of the element. 

In chemical analysis and calculation the weights of reacting substances are considered through the molecules and atoms of the substances taking part in the chemical reaction. The term mole indicates at the same time the weight of the reacting substances as well as the number of molecules present in them. Here lies the significance of mole. 

Besides, mole is also used to represent one gram ion and one Faraday of electricity. 

One mole of nitrogen molecules means one gram molecule of nitrogen or 28 gram of nitrogen or 6.023 x 10 molecules of nitrogen. 

One mole of ammonium ions means one gram ion of ammonium ions or 18 grams of ammonium ions or 6.023 x 10 ammonium ions. 

---

If these assumptions are valid, however, stoichiometric calculations provide a reliable basis for quantitative predictions. It is important to be able to make these calculations with ease. Fortunately, they all can be made with a single pattern based upon the mole concept. 

The initial set of experiments and the first few textbook chapters lay down a foundation for the course. The elements of scientific activity are immediately displayed, including the role of uncertainty. The atomic theory, the nature of matter in its various phases, and the mole concept are developed. Then an extended section of the course is devoted to the extraction of important chemical principles from relevant laboratory experience. The principles considered include energy, rate and equilibrium characteristics of chemical reactions, chemical periodicity, and chemical bonding in gases, liquids, and solids. The course concludes with several chapters of descriptive chemistry in which the applicability and worth of the chemical principles developed earlier are seen again and again. 

Sub-micro representations are used extensively in teaching the mole concept, stoichiometiy, solubihty and chemical equilibrium at UCT. Having students draw and annotate chemical diagrams representing chemical phenomena at the sub-micro level can provide some insight into their understanding of chemistiy at the macro level. The following examples are typical of the questions used to probe links between the sub-micro and symbohc levels of representations as part of the assessment practice for this course. For example, students were asked to balance the equation shown in Fig. 8.7. 

We developed the concept of the mole In terms of pure chemical substances, but many chemical reactions take place In solution. To treat solution reactions quantitatively, we need ways to apply the mole concept to solutions. A substance used to dissolve solutes Is a solvent, and a pure substance dissolved In solution Is a solute. Most of the time, the solvent Is a liquid and Is present In much larger quantities than any solutes. 

How can the mole concept be used to predict the limiting reactant in a chemical reaction ... 

Mass and volume relations with emphasis on the mole concept, including empirical formulas and limiting reactants... 

This is a critical chapter in your study of chemistry. Our goal is to help you master the mole concept. You will learn about balancing equations and the mole/mass relationships (stoichiometry) inherent in these balanced equations. You will learn, given amounts of reactants, how to determine which one limits the amount of product formed. You will also learn how to determine the empirical and molecular formulas of compounds. All of these will depend on the mole concept. Make sure that you can use your calculator correctly. If you are unsure about setting up problems, refer back to Chapter 1 of this book and go through Section 1-4, on using the Unit Conversion Method. Review how to find atomic masses on the periodic table. Practice, Practice, Practice. 

It is possible to expand these examples to any titration problem, acid-base, redox, precipitation, and so on. Just remember that the key is the mole concept. 

Our goal in this chapter is to assist you in learning the concepts of gases and gas laws. Be sure that you know how to properly use your calculator and, if you need to, refer to Chapter 3 on the mole concept. It s especially true with gas law problems that the only way to master them is to Practice, Practice, Practice. 

In this chapter, we will help you learn about the energy changes, especially heat, which occurs during both physical and chemical changes. You might need to review the Unit Conversion Method in Chapter 1 and the sections in Chapter 3 on balancing chemical reactions and the mole concept if you are not comfortable with them already. And remember to Practice, Practice, Practice. 

The major goal of this chapter is to help you master the concepts associated with solutions—concentration units, solubility, and especially colligative properties. We will also examine the properties of colloids. If you are still unsure about calculations and the mole concept, review Chapters 1,3, and 4. And again, the only way to master these concepts is to Practice, Practice, Practice. 

Our goal in this chapter is to help you understand how to balance redox equations, know the different types of electrochemical cells, and how to solve electrolysis problems. Have your textbook handy—you may need to find some information in electrochemical tables. We will be using the mole concept, so if you need some review refer to Chapter 3, especially the mass/mole relationships. You might also need to review the section concerning net-ionic equations in Chapter 4. And don t forget to Practice, Practice, Practice. 

A production chemist is interested primarily in the macroscopic world, not the microscopic one of atoms and molecules. Even a chemistry student working in the laboratory will not be weighing out individual atoms and molecules, but large numbers of them in grams. There must be a way to bridge the gap between the microscopic world of individual atoms and molecules, and the macroscopic world of grams and kilograms. There is—it is called the mole concept, and it is one of the central concepts in the world of chemistry. 

The actual number of atoms in one mole of an element has been determined by several elegant experimental procedures to be 6.02 X 10 This quantity is known as Avogadro s number, in honor of one of the pioneers of the atomic theory. One can then see that one mole of carbon atoms (12.01 grams) will contain exactly the same number of atoms as one mole (55.85 grams) of iron. Using the mole concept, the chemist can now go into the laboratory and weigh out equal quantities of atoms of the various elements. 

Mixture, stoichiometric, 17 Moisture 88 Mole concept, 15-17 Molecular weight, 16 Molybdenum, 132... 

Students will explain the mole concept and use this concept to prepare chemical solutions of particular molarities. 

During this procedure, your teacher will introduce the mole concept. Use a periodic table to find the relative masses of all the elements in the molecule CuS04 and K2Cr04, respectively Cu (copper), S (sulfur) and O (oxygen) and K (potassium), Cr (chromium), O (oxygen). The relative mass in grams for any element contains the same number of atoms. This number of atoms, 6.02 x 1023, is called a mole. In the preparation of any 0.1 M solution, 0.1 mole of molecules is needed. A 0.1 M solution, by definition, contains 0.1 mole of a substance dissolved in 1.0 liter of a solvent. 

Several topics are suggested here that could be de-emphasized or eliminated, affording instructors time to explore biochemical topics more fully electron configuration, quantum numbers, atomic orbitals, the mole concept, limiting reactant and stoichiometry, organic nomenclature, and organic reactions by functional group. 

Using the mole concept and the periodic table, you can determine the mass of one mole of a compound. You know, however, that one mole represents 6.02 x 1023 particles. Therefore you can use a balance to count atoms, molecules, or formula units ... 

In this chapter, you have learned about the relationships among the number of particles in a substance, the amount of a substance in moles, and the mass of a substance. Given the mass of any substance, you can now determine how many moles and particles make it up. In the next chapter, you will explore the mole concept further. You will learn how the mass proportions of elements in compounds relate to their formulas... 

Assume that your friend has missed several chemistry classes and that she has asked you to help her prepare for a stoichiometry test. Unfortunately, because of other commitments, you do not have time to meet face to face. You agree to email your friend a set of point-form instructions on how to solve stoichiometry problems, including those that involve a limiting reactant. She also needs to understand the concept of percentage yield. Write the text of this email. Assume that your friend has a good understanding of the mole concept. 

---