Mole converting between number

The amounts of atoms, ions, or molecules in a sample are expressed in moles, and Avogadro s constant, NA, is used to convert between numbers of these particles and the numbers of moles. 

We can inter-convert between number of moles and concentration here because the reactions are performed within a constant volume of solvent. 

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

For work in the laboratory, it s necessary to weigh reactants rather than just know numbers of moles. Thus, it s necessary to convert between numbers of moles and numbers of grams by using molar mass as the conversion factor. The molar mass of any substance is the amount in grams numerically equal to the substance s molecular or formula mass. Carrying out chemical calculations using these relationships is called stoichiometry. 

Mass and number of entities relate directly to number of moles, not to each other. Therefore, to convert between number of entities and mass, r5/ convert to number of moles. For example, to find the number of atoms in a given mass. 

Convert between number of moles and the mass of an element. 

Co to http //now.brookscole.com/ cracolice3e and click Coached Problems for a step-by-step tutorial on Converting Between Numbers of Atoms and Moles. 

Converting between Number of Moles and Number of Atoms... 

Converting between number of moles and number of atoms is similar to converting between dozens of eggs and number of eggs. For eggs, you use the conversion factor 1 dozen eggs = 12 eggs. For atoms, you use the conversion factor 1 mol atoms =... 

STRATEGIZE The conceptual plan has the form volume A amount A (in moles) amount B (in moles) —> volume B. Use the molar concentrations of the KCl and Pb(N03)2 solutions as conversion factors between the number of moles of reactants in these solutions and their volumes. Use the stoichiometric coefficients from the balanced equation to convert between number of moles of Pb(N03)2 and number of moles of KCl. 

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

As emphasized in Section 2-, many of the calculations in chemistry involve converting back and forth among the mass of a substance, the number of moles, and the number of atoms and/or molecules. These calculations are all centered on the mole. The connections shown in Figure apply to chemical compounds as well as to atoms of pure elements. Molar mass and Avogadro s number provide links between mass of a sample, the number of moles, and the number of molecules. 

To convert between molarity and the other mole-based concentration measures, we must relate volume to mass and number of moles. Whereas molar mass lets us convert between mass and moles, we need density to convert... 

Making particle numbers manageable with Avogadro s number Converting between masses, mole counts, and volumes Dissecting compounds with percent composition Moving from percent composition to empirical and molecular formulas... 

Convert between mass and number of moles by using the molar mass, Examples E.2 and E.4. 

We saw in Section 3.3 that the coefficients in a balanced equation tell the numbers of moles of substances in a reaction. In actual laboratory work, though, it s necessary to convert between moles and mass to be sure that the correct amounts of reactants are used. In referring to these mole-mass relationships, we use the word stoichiometry (stoy-key-ahm-uh-tree from the Greek stoicheion, "element," and metron, "measure"). Let s look again at the reaction of ethylene with HC1 to see how stoichiometric relationships are used. 

In the previous Sample Problem, you saw how to convert moles to mass. Often, however, chemists know the mass of a substance but are more interested in knowing the number of moles. Suppose that a reaction produces 223 g of iron and 204 g of aluminum oxide. The masses of the substances do not tell you very much about the reaction. You know, however, that 223 g of iron is 4 mol of iron. You also know that 204 g of aluminum oxide is 2 mol of aluminum oxide. You may conclude that the reaction produces twice as many moles of iron as it does moles of aluminum oxide. You can perform the reaction many times to test your conclusion. If your conclusion is correct, the mole relationship between the products will hold. To calculate the number of moles in a sample, find out how many times the molar mass goes into the mass of the sample. 

Converting Between Moles, Mass, and Number of Particles... 

Now that you have learned how the number of particles, number of moles, and mass of a substance are related, you can convert from one value to another. Usually chemists convert from moles to mass and from mass to moles. Mass is a property that can be measured easily. The following graphic shows the factors used to convert between particles, moles, and mass. Moles are a convenient way to communicate the amount of a substance. 

You now know what a balanced chemical equation tells you in terms of number of particles, number of moles, and mass of products and reactants. How do you use this information Because reactants and products are related by a fixed ratio, if you know the number of moles of one substance, the balanced equation tells you the number of moles of all the other substances. In Chapters 5 and 6, you learned how to convert between particles, moles, and mass. Therefore, if you know the amount of one substance in a chemical reaction (in particles, moles, or mass), you can calculate the amount of any other substance in the reaction (in particles, moles, or mass), using the information in the balanced chemical equation. 

This last example uses a dimensional analysis to convert between moles, mass, and volume. How many liters will 150 grams of S02(g) occupy at STP Remember the importance of keeping careful track of the numbers, units, and substance in a problem such as this one. Start by converting to moles and then to volume ... 

The mole is defined as the number of atoms in exactly 12 g of which is 6.02 X 10 —Avogadro s number. Equal numbers of moles of two (or more) different substances have the same number of formula units but not the same mass. The molar mass is the mass in grams of one mole of a substance. The number of grams per mole—the molar mass— is a frequently used conversion factor, used for converting between grams and moles. (Section 7.3)... 

Avogadro s number may be used to count any kind of particle, including atoms and molecules. For calculations in this book, Avogadro s number will be rounded to 6.022 x particles per mole. Skills Toolkit 1 shows how to use Avogadro s number to convert between amount in moles and the number of particles. 

Use Avogadro s number to convert between amount in moles and number of particles. 

Solve problems converting between mass, amount in moles, and number of particles using Avogadro s number and molar mass. 

These conversion factors can be used to convert between a number of moles of substance and a corresponding number of molecules. For example, imagine that you want to convert 2.66 mol of a compound into the corresponding number of molecules. How do you know which conversion factor to use Skills Toolkit 1 can help. 

Example Problem 11-8 illustrated how to find the number of moles of a compound contained in a given mass. Now, you will learn how to calculate the number of representative particles—molecules or formula units—contained in a given mass and, in addition, the number of atoms or ions. Recall that no direct conversion is possible between mass and number of particles. You must first convert the given mass to moles by multiplying by the inverse of the molar mass. Then, you can convert moles to the number of representative particles by multiplying by Avogadro s number. To determine numbers of atoms or ions in a compound, you will need conversion factors that are ratios of the number of atoms or ions in the compound to one mole of compound. These are based on the chemical formula. Example Problem 11-9 provides practice in solving this type of problem. 

One of the most important applications of the gas laws in chemistry is to calculate the volumes of gases consumed or produced in chemical reactions. If the conditions of pressure and temperature are known, the ideal gas law can be used to convert between the number of moles and gas volume. Instead of working with the mass of each gas taking part in the reaction, we can then use its volume, which is easier to measure. This is illustrated by the following example. 

Unfortunately, natural carbon always contains carbon-13 atoms as well as carbon-12 atoms, so the conversion factor shown above is not very useful. We need a conversion factor that relates mass and moles of natural carbon instead. Because the average mass of the atoms in natural carbon (12.011 u) is slightly greater than the mass of each carbon-12 atom (12 u), the mass of a mole of natural carbon atoms has a mass slightly greater than the mass of a mole of carbon-12 atoms (12.011 g compared to 12 g). The following conversion factor can be used to convert between mass of natural carbon and number of moles of carbon atoms. 

The number of grams in the molar mass of an element is the same as the atomic mass. Translating atomic masses into molar masses, you can construct conversion factors that convert between the mass of an element and the number of moles of the element. 

Example 9.2 shows how an atomic mass translates into a molar mass that allows us to convert between mass of an element and number of moles of that element. 

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