Particles mole concept

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... 

Concept Mapping Design a concept map that illustrates the mole concept. Include moles, Avogadro s number, molar mass, number of particles, percent composition, empirical formula, and molecular formula. 

In this chapter, you learned to solve several kinds of stoichiometric problems. For each kind, you used the mole concept because when substances react, their particles interact. The number of particles at this sub-microscopic level controls what happens macroscopicaUy. In the next chapter, you will use the mole concept and the particle nature of matter to study the mixtures of substances called solutions. 

Interconversion between numbers of moles, particles, and grams. The mole concept is central to chemical calculations involving measured quantities of matter. 

The mole concept is the key to both stoichiometry and gas laws. A mole is a definite amount of substance. Mole is a unit based on the number of identities (i.e. atoms, molecules, ions, or particles). A mole of anything has the same number of identities as the number of atoms in exactly 12 grams of carbon-12, the most abundant isotope of carbon. 

The mole concept provides the bridge between mass and number of particles. To illustrate how this bridge works, let s calculate the number of copper atoms in an old copper penny. Such a penny has a mass of about 3 g, and we assume it is 100% copper ... 

In a strict sense, 1 mol is a specific number of particles. However, in chemistry it is customary to follow the useful practice of also letting 1 mol stand for the mass of a sample of element or compound that contains Avogadro s number of particles. Thus, the application of the mole concept to sulfur (at. wt. = 32.1 u) gives the following relationships ... 

The mole concept can also be applied to particles that are molecules instead of atoms. The compound carbon dioxide consists of molecules that contain one carbon atom, C, and two oxygen atoms, O. The formula for the molecule is CO2. The molecular weight of the molecule is calculated as shown earlier by adding together the atomic weight of one carbon atom and the atomic weight of two oxygen atoms ... 

The mole is often referred to as a chemist s unit of quantity. Counting atoms is a difficult process and beyond the scope of most calculators, but measuring the mass of a sample is easy when we can relate the number of atoms in a sample to its mass. This is the unique purpose of the mole. A mole of any substance is its molecular formula weight expressed in grams. Avogadro s number s a universal constant that states the number of molecules in a mole Nq = 6.023 x 10 molecules/mole. One mole (abbreviated mol) of any element (chemical compound) has the same number of chemical particles as one mole of another element (chemical compound). In other words, 1 mole of any compound contains 6.02 x 10 molecules. Review the following problem using the mole concept. 

A summary of the mole concept applied to different particles... 

Avogadro s number is the number of particles (atoms, molecules,. or formula units) that are in a mole of a substance. In this lab, you will relate a common object to the concept of Avogadro s number by finding the mass and volume of one mole of the object. 

The mole is the most important concept in this chapter. Nearly every problem associated with this material requires moles in at least one of the steps. You should get into the habit of automatically looking for moles. There are several ways of finding the moles of a substance. You may determine the moles of a substance from a balanced chemical equation. You may determine moles from the mass and molecular weight of a substance. You may determine moles from the number of particles and Avogadro s number. You may find moles from the moles of another substance and a mole ratio. Later in this book, you will find even more ways to determine moles. In some cases, you will be finished when you find moles, in other cases, finding moles is only one of the steps in a longer problem. 

Physiologists studying osmotic relationships of organisms, however, are often concerned with the total concentration of all dissolved substances, not just the concentrations of specific solutes. For expressing the total number of osmotically active particles in a solution, the concept of osmolality is commonly employed to refer to the osmotic pressure characteristic of a solution. One osmole is defined as the osmotic pressure of a 1.0 molal solution of an ideal solute. Because conditions of ideality do not pertain to the case of biological fluids, it is not possible to extrapolate precisely from chemical determinations of moles of solute per kilogram (or liter) of fluid to the osmolality of that fluid. Rather, this value must be determined empirically. 

Avogadro s principle tells us that equal volumes of gases, at equal temperatures and pressures, contain an equal number of particles. It is from this principle that chemists have developed the concept of the molar volume of gases. It has been determined that one mole of any gas at standard temperature and pressure (a temperature of 273 K and 101.3 kPa of pressure) will occupy 22.4 dm3 of volume. This allows us to determine the number of moles in a gas, provided we know the volume, temperature, and pressure of the sample. 

Visuahzing a mole as a pile of particles, however, is just one way to understand this concept. A sample of a substance has a mass, volume (generally used with gases), and number of particles that is proportional to the chemical amount (measured in moles) of the sample. For example, one mole of oxygen gas (O2) occupies a volume of 22.4 L at standard temperature and pressure (STP 0°C and 1 atm), has a mass of 31.998 grams, and contains about 6.022 X 10 molecules of oxygen. Measuring one of these quantities allows the calculation of the others and this is frequently done in stoichiometry. 

The concept of molar mass enables chemists to measure the number of submicroscopic particles in a sample without counting them directly simply by determining the chemical amount of a sample. To find the chemical amount of a sample, chemists measure its mass and divide by its molar mass. Multiplying the chemical amount (in moles) by Avogadro s constant (Aa) yields the number of particles present in the sample. 

Some people think that Amedeo Avogadro (1776-1856) determined the number of particles in a mole and that is why the quantity is known as Avogadro s number. In reafity Avogadro built a theoretical foundation for determining accurate atomic and molecular masses. The concept of a mole did not even exist in Avogadro s time. 

In the previous section, the chemical potential of species / in a given phase was defined as the work needed to bring a mole of that species from infinity into the bulk of that phase. This concept is of limited validity for ceramics, however, since it only applies to neutral specie or uncharged media, where in either case the electric work is zero. Clearly, the charged nature of ceramics renders that definition invalid. Instead the pertinent function that is applicable in this case is the electrochemical potential defined for a particle of net charge z, by ... 

Design a concept map that shows the conversion factors needed to convert between mass, moles, and number of particles. 

A mole always contains Key Concepts the same number of particles however, moles of different substances have different masses. 

The concept of the mole is considered one of the most characteristic quantitative concepts in chemistry among the seven SI units, it is the only one found in chemistry. Furio, Azcona Ratcliffe (2000) found, by using a questionnaire-based enquiry with a group of 36 prospective chemistry teachers and 47 experienced chemistry teachers from Spain, that most members of each group interpreted the mole primarily as a (certain) number of particles, while most of the remaining members of each group considered... 

In a complex apparatus, Gimesch and Schneider [30, 119] studied the suspension polymerization of vinyl acetate. Their procedure involved equipment which automatically added tempered water to the reacting system as heat was evolved as a result of the polymerization process. Thus they maintained isothermal reaction conditions. The rate of reaction could be followed by recording the water uptake of the equipment with time. The heat of polymerization was also determined (found to be 23 kcal/mole which was considered a satisfactory check of the literature value which is scattered around 21.4 kcal/mole). From this work, a somewhat different mechanism of the suspension polymerization process emerges than the widely accepted concept of the water-cooled bulk polymerization of small particles. It was noted that with an increase in the initiator concentration, there was the expected increase in polymerization rate. With increasing stirring rate, the rate of polymerization decreased. Along with the suspension polymerization, there was always a certain amoimt of imdesirable emulsion polymerization. It was postulated that in the process, free radicals, formed in a monomer drop may be extracted into the aqueous phase where they may act on dissolved vinyl acetate by kinetic processes unique to this system and different from the conventional mechanism of suspension polymerization. 

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