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Counting Particles of Matter and Using Moles in Stoichiometry

Learn how to count particles of matter using Avogadro's principle and relate it to weighing samples. Understand the concept of stoichiometry and solve stoichiometric problems using molar mass. Explore the use of mole ratios to predict quantities of reactants and products in chemical reactions.

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Counting Particles of Matter and Using Moles in Stoichiometry

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  1. Chapter Menu Section 12.1Counting Particles of Matter Section 12.2 Using Moles Click a hyperlink to view the corresponding slides. Chapter Menu

  2. Counting Particles of Matter Define the mole as a counting number. Relate counting particles to weighing samples of substances. Solve stoichiometric problems using molar mass. Section 12.1

  3. Counting Particles of Matter Avogadro’s principle: equal volumes of gases at the same temperature and pressure contain equal numbers of particles Section 12.1

  4. Counting Particles of Matter stoichiometry mole Avogadro’s number molar mass molecular mass formula mass A mole always contains the same number of particles; however, moles of different substances have different masses. Section 12.1

  5. Stoichiometry Stoichiometry is the study of quantitative relationships between reactants and products in a chemical reaction. Section 12.1

  6. Stoichiometry (cont.) The group or unit of measure used to count number of atoms, molecules, ions, or formula units is the mole (abbreviated mol). The number of things in a mole is 6.02 × 1023 and is called Avogadro’s number. Section 12.1

  7. Molar Mass Using moles, macroscopic measurements, such as mass, can be related to the molecules involved in a chemical reaction. The mass of one mole of a pure substance is called its molar mass. Section 12.1

  8. Molar Mass (cont.) The molar mass of an element is simply the average atomic mass of that element stated in grams rather than atomic mass units. Section 12.1

  9. Molar Mass (cont.) The molecular mass of a covalent compound is the mass in atomic mass units of one molecule. • Its molar mass is the mass in grams of one mole of its molecules. Section 12.1

  10. Molar Mass (cont.) The formula mass of an ionic compound is the mass in atomic mass units of one formula unit. • Its molar mass is the mass in grams of one mole of its formula units. Section 12.1

  11. Molar Mass and Stoichiometry The concept of molar mass makes it easy to determine the number of particles in a sample of a substance by simply measuring the mass of the sample. Use the molar mass to convert mass to moles or moles to mass. Section 12.1

  12. Section Assessment What does the mole measure? A.mass of a substance B.density of a gas C.volume of a gas D.amount of a substance Section 12.1

  13. Section Assessment Molar mass is used to convert what? A.mass to moles B.atomic weight C.moles to mass D.particles Section 12.1

  14. End of Section 12.1

  15. Using Moles Predict quantities of reactants and products in chemical reactions. Determine mole ratios from formulas for compounds. Identify formulas of compounds by using mass ratios. Section 12.2

  16. Using Moles mole: group or unit of measure used to count numbers of atoms, molecules, or formula units of a substance Section 12.2

  17. Using Moles molar volume ideal gas law theoretical yield percent yield empirical formula Balanced chemical equations relate moles of reactants to moles of products. Section 12.2

  18. Using Molar Masses in Stoichiometric Problems Balanced chemical equations and moles can be used to predict the masses of reactants or products. Section 12.2

  19. Using Molar Masses in Stoichiometric Problems (cont.) Section 12.2

  20. Using Molar Volumes in Stoichiometric Problems The molar volume of a gas is the volume that a mole of gas occupies at a pressure of one atmosphere (equal to 101 kPa) and a temperature of 0.00°C. Section 12.2

  21. Ideal Gas Law The ideal gas law describes the behavior of an ideal gas in terms of pressure (P), volume (V), temperature (T), and number of moles of gas, n. PV = nRT (R represents the ideal gas constant) Section 12.2

  22. Theoretical Yield and Actual Yield The amount of product of a chemical reaction predicted by stoichiometry is called the theoretical yield. The percent yield of a reaction is the ratio of the actual yield to the theoretical yield. Section 12.2

  23. Composition of Geraniol Determining Mass Percents Percent composition of a compound can be determined from its chemical formula. Section 12.2

  24. Determining Chemical Formulas To determine a chemical formula, find the relative numbers of each of the atoms in the formula unit of the compound. The formula of a compound having the smallest whole-number ratio of atoms in the compound is called the empirical formula. Section 12.2

  25. Determining Chemical Formulas (cont.) Section 12.2

  26. Determining Chemical Formulas (cont.) The empirical formula of a compound can be determined from its percent composition. You can calculate the empirical formula from percent by mass by assuming you have 100.00 g of the compound. Then, convert to mass of each element to moles. Section 12.2

  27. Determining Chemical Formulas (cont.) Chemical formulas for most ionic compounds are the same as their empirical formulas. However, the empirical formula is not always the chemical formula. Section 12.2

  28. Determining Chemical Formulas (cont.) Many different covalent compounds have the same empirical formulas because atoms can share electrons in different ways. The chemical formula of a compound can be determined if the molar mass and the empirical formula are known. Section 12.2

  29. Section Assessment Two substances have the same percent by mass composition, but very different properties. They must have the same: A.density B.empirical formula C.molecular formula D.molar mass Section 12.2

  30. Section Assessment The ___ describes the behavior of an ideal gas in terms of pressure (P), volume (V), temperature (T), and number of moles of gas, n. A.theoretical yield B.absolute yield C.empirical formula D.atomic mass Section 12.2

  31. End of Section 12.2

  32. Chemistry Online Study Guide Chapter Assessment Standardized Test Practice Image Bank Concepts in Motion Resources Menu

  33. Key Concepts Stoichiometry relates the amounts of products and reactants in a chemical equation to one another. The mole is a unit used to count particles of matter. One mole of a pure substance contains Avogadro’s number of particles, 6.02 x 1023. Molar mass can be used to convert mass to moles or moles to mass. Study Guide 1

  34. Key Concepts A balanced chemical equation provides mole ratios of the substances in the reaction. The ideal gas law is expressed in the following equation PV=nRT. Percent yield measures the efficiency of a chemical reaction. Percent composition can be determined from the chemical formula of a compound; the empirical formula of a compound can be determined from its percent composition. The chemical formula of a compound can be determined if the molar mass and the empirical formula are known. Study Guide 2

  35. The mass in grams of 1 mol of any pure substance is: A.atomic mass B.Avogadro’s number C.1 g/mol D.molar mass Chapter Assessment 1

  36. What does Avogadro’s number represent? A.the number of atoms in 1 mol of an element B.the number of molecules in 1 mol of a compound C.the number of Na+ ions in 1 mol of NaCl (aq) D.all of the above Chapter Assessment 2

  37. A chemical reaction equation must be ___ in order to make stoichoimetric calculations. A.measured B.controlled C.balanced D.empirical Chapter Assessment 3

  38. ___ is important in the cost effectiveness of many industrial manufacturing processes. A.Percent yield B.Theoretical yield C.Molar volume D.Molar mass Chapter Assessment 4

  39. The SI base unit of amount is ___. A.the gram B.the kilogram C.the mole D.Avogadro’s number Chapter Assessment 5

  40. The molar mass of an element is numerically equivalent to what? A.1 mole B.its atomic mass C.its atomic number D.Avogadro’s number STP 1

  41. When actual yield is less than theoretical yield, the efficiency of the reaction is expressed as: A.percent yield B.molar volume C.molecular mass D.molar mass STP 2

  42. Which is the empirical formula for hydrogen peroxide? A.H2O2 B.H2O C.HO D.none of the above STP 3

  43. The ___ is the maximum amount of products that can be produced from a given amount of reactant. A.atomic mass B.absolute yield C.empirical formula D.theoretical yield STP 4

  44. Why do many different covalent compounds have the same empirical formulas? A.because atoms can share electrons in different ways B.because they have the same number of moles C.because they have the same percent yields D.because they have the same elements STP 5

  45. Click on an image to enlarge. IB Menu

  46. IB 1

  47. IB 2

  48. IB 3

  49. Composition of Geraniol IB 4

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