Moles Avogadro constant

In terms of moles, Avogadro s hypothesis can be stated The same volume is occupied by one mole of any gas at a given temperature and pressure. The number of molecules in one mole is known as the Avogadro number constant. ... 

The Avogadro constant is the number of particles contained in one mole of a substance. Its value is 6.02 x 1023 mob1 and its symbol is L. In one mole of the carbon-12 isotope, there are 6.02 x 1023 12C atoms. 

One mole of any element contains 6.022x 1023 atoms, the Avogadro constant. 

In these problems we use the Avogadro constant and the fact that one mole of atoms of an element has a weight in grams equal to its atomic mass. 

One mole of electrons carries a charge o/ L x e, where e is the charge on a single electron and L is the Avogadro constant. This quantity of charge (L X ej has a value of 96 487 C, and is known as the Faraday constant F, and so we talk in terms of faradays of charge . The basic reaction at an electrode is electron transfer to effect reduction (the analyte gains electrons) or oxidation (the analyte loses electrons), as follows ... 

AVOGADRO CONSTANT. The number of molecules contained in one mole or gram-molecular weight of a substance. The most recent value is 6.0220943 x lO23 6.3 x 1017. In measurements made by scientists at the National Bureau of Standards (Gaithersburg, Maryland) and announced in late 1974. the uncertainty (as compared with previous determinations) of the number was reduced hy a factor of 30. 

The number of objects per mole, 6.0221 X 1023 mol 1, is called the Avogadro constant, NA, in honor of the nineteenth-century Italian scientist Amedeo Avogadro (Fig. E.3), who helped to establish the existence of atoms. The Avogadro constant is used to convert between the number of moles and the number of atoms, ions, or molecules ... 

Thus, from a straightforward measurement of mass, we know the number of moles of atoms present in the sample (if desired, the actual number of atoms can be calculated by multiplying the number of moles by the Avogadro constant). 

The molar masses of elements are determined by using mass spectrometry to measure the masses of the individual isotopes and their abundances. The mass per mole of atoms is the mass of an individual atom multiplied by the Avogadro constant (the number of atoms per mole). However, there is a complication. Most elements occur in nature as a mixture of isotopes we saw in Section B, for instance, that neon occurs as three isotopes, each with a different mass. In chemistry, we almost always deal with natural samples of elements, which have the natural abundance of isotopes. So, we need the average molar mass, the molar mass calculated by taking into account the masses of the isotopes and their relative abundances in typical samples. All molar masses quoted in this text refer to these average values. Their values are given in Appendix 2D. They are also included in the periodic table inside the front cover and in the alphabetical list of elements inside the back cover. 

STRATEGY First, calculate the average mass of the isotopes by adding together the individual masses, each multiplied by the fraction that represents its abundance. Then obtain the molar mass, the mass per mole of atoms, by multiplying the average atomic mass by the Avogadro constant. 

Use the Avogadro constant to convert between number of moles and the number of atoms, molecules, or ions in a sample, Example E.l. 

In the last step, we used the relation In 2 = 1 - f + j — + . Finally, we multiply 1 by 2 to obtain the total energy arising from interactions on each side of the ion and then by the Avogadro constant, NA, to obtain an expression for the lattice energy per mole of ions ... 

The total number of molecules, N, is the product of the number of moles, n, and the Avogadro constant, NA, so the last equation becomes... 

We have used M = mNA in the last step. The molar kinetic energy of an ideal gas is the mean energy of a molecule (the quantity we have just calculated) multiplied by the number of molecules per mole (the Avogadro constant). Therefore,... 

The Faraday constant, F, is the magnitude of the charge per mole of electrons (the product of the elementary charge e and the Avogadro constant... 

Avogadro constant The number of objects per mole of objects (Na = 6.022 14 X 1023 mol-1). Avogadro s number is the number of objects in one mole of objects (that is, the dimensionless number 6.022 14 X 1023). Avogadro s principle The volume of a sample of gas at a given temperature and pressure is proportional to the amount of gas molecules in the sample V n. axial bond A bond that is perpendicular to the molecular plane in a bipyramidal molecule, axial lone pair A lone pair lying on the axis of a bipyramidal molecule. 

When other kinds of work are involved, it is necessary to specify more variables, but the point is that when a small number of properties are specified, all the other properties of the system are fixed. This is in contrast with the very large number of properties that have to be specified to describe the microscopic state of a macroscopic system. In classical physics the complete description of a mole of an ideal gas would require the specification of 3NA components in the three directions of spatial coordinates and 3NA components of velocities of molecules, where NA is the Avogadro constant. 

One mole (1 mol) of a substance contains 6.022 141 99 x 1023 particles of the substance. This value is called the Avogadro constant. Its symbol is Na. 

Chemists have devised various ways to determine the Avogadro constant. To learn more about how this constant has been found in the past and how it is found today, go to the web site above. Go to Science Resources, then to Chemistry 11 to find out where to go next. What are some methods that chemists have used to determine the number of particles in a mole How has the accepted value of the Avogadro constant changed over the years ... 

In the Thought Lab below, you can practise working with the mole by relating the Avogadro constant to familiar items. Normally the mole is used to group atoms and compounds. For example, chemists know that 1 mol of barium contains 6.02 x 1023 atoms of Ba. Similarly, 2 mol of barium sulfate contain 2 x (6.02 x 1023) = 12.0 x 1023 molecules of BaS04. 

The mole is used to help us count atoms and molecules. The relationship between moles, number of particles, and the Avogadro constant is... 

N = number of particles n = number of moles Na = Avogadro constant N = nx Na... 

Go to the Chemistry 11 Electronic Learning Partner for a video clip that describes the principles behind the Avogadro constant and the mole. 

To learn how many moles are in a substance when you know how many particles are present, find out how many times the Avogadro constant goes into the number of particles. 

The Avogadro constant is the factor that converts the relative mass of individual atoms or molecules, expressed in atomic mass units, to mole quantities, expressed in grams. 

The molar mass relates the amount of an element or a compound, in moles, to its mass. Similarly, the Avogadro constant relates the number of particles to the molar amount. 

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