Mole converting between moles

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. 

The correct answer is (B). This is a mole-to-mole conversion. If you have a balanced equation to start, you can solve these in your head. The mole ratios from the balanced equation allow you to quickly convert between moles of substances. The ratio of Cl2 to SiCl4 is 2 to 1. That means you will produce only half as many moles of SiCl4, or 1.92 mol. You can also solve the problem using a formula, as shown below ... 

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

Use the Avogadro constant to convert between moles and particles. 

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 ... 

This example can be extended by asking What mass of carbon dioxide is produced when 96.1 grams of propane is combusted with oxygen In this case we must convert between moles of propane and moles of carbon dioxide. This conversion can be done by inspecting the balanced equation, which shows that 3 moles of CO2 is produced for each mole of C3H8 reacted ... 

To convert between moles and grams, chemists use the molar mass of a substance. The molar mass of an element is the mass in grams of one mole of the element. Molar mass has the unit grams per mol (g/mol). The mass in grams of 1 mol of an element is numerically equal to the element s atomic mass from the periodic table in atomic mass units. For example, the atomic mass of copper to two decimal places is 63.55 amu. Therefore, the molar mass of copper is 63.55 g/mol. Skills Toolkit i shows how to convert between moles and mass in grams using molar mass. 

Additive or group contribution techniques are commonly used to predict the properties of polymers from their molecular structures. These techniques provide many extremely useful simple correlations to predict the properties. Group contribution techniques will be reviewed briefly in Section l.B. The main approach used in the scheme of correlations developed in this book is based on topological techniques. The philosophy of this approach, and the scope of the work presented in this book, will be discussed in Section l.C. The detailed technical implementation of the scheme of correlations will be postponed to later chapters. Equations for converting between mole, weight and volume fractions will be listed in Section l.D. The subjects which will be covered in the later chapters will be summarized in Section l.E. 

To complete these steps, we need one additional kind of conversion factor that converts between moles of an element and moles of a compound containing that element. We obtain this conversion factor from the compound s chemical formula. For example, the formula for hexane, C6H14, tells us that each hexane molecule contains six... 

Similarly, we can use ionic formulas to generate conversion factors that convert between moles of atoms of each element in an ionic compound and moles of compound. For example, the formula for calcium nitrate, Ca(N03)2, yields the following conversion factors. 

We can convert between moles of element and moles of a compound containing that element by using the molar ratio derived from the... 

Write a conversion factor that converts between moles of nitrogen in nitrogen pentoxide, N2O5, and moles of N2O5. 

Use molarity to convert between moles of solute and volume of solution. 

Write a conversion factor that could be used to convert between moles of antimony pentafluoride, SbF5, and moles of fluorine, F2. 

There are several ways to convert between moles of a gaseous substance and its volume. One approach is to use as a conversion factor the molar volume at STP. STP stands for standard temperature and pressure. Standard temperature is 0 °C, or 273.15 K, standard pressure is 1 atm, or 101.325 kPa, or 760 mmHg. The molar volume, or... 

Because the ideal gas equation applies to all ideal gases, the molar volume at STP applies to all gases that exhibit the characteristics of the ideal gas model. In equation stoichiometry, the molar volume at STP is used in much the way we use molar mass. Molar mass converts between moles and the measurable property of mass molar volume at STP converts between moles and the measurable property of volume of gas. Note that while every substance has a different molar mass, all ideal gases have the same molar volume at STP. Example 13.5 provides a demonstration. 

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