1 / 12

Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas. Average Atomic Mass and the Periodic Table. You have learned that you can use atomic masses on the periodic table to find the molar mass of elements. Many of these values on the periodic

grace-travis
Download Presentation

Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas Average Atomic Mass and the Periodic Table You have learned that you can use atomic masses on the periodic table to find the molar mass of elements. Many of these values on the periodic table are close to whole numbers. However, most atomic masses are written to at least three places past the decimal. Most Elements Are Mixtures of Isotopes You remember that isotopes are atoms that have different numbers of neutrons than other atoms of the same element do. So, isotopes have different atomic masses. The periodic table reports a average atomic mass weighted average of the atomic mass of an element’s isotopes. A weighted average takes into account the relative importance of each number in the average. Thus, if there is more of one isotope in a typical sample, it affects the

  2. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas Remember from Chapter 3 the formula to calculate the average atomic mass (mass of atom1 x % quantity1) + (mass of atom2 x % quantity2) +…….. Average Atomic Mass = 100 Calculate the average atomic mass of Copper using the information below. • atomic mass of a Cu-63 atom = 62.94 amu • abundance of Cu-63 = 69.17% • atomic mass of Cu-65 = 64.93 amu • abundance of Cu-65 = 30.83%

  3. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas (62.94 x 69.17) + (64.93 x 30.83) Mass of Copper = 100 63.55 amu

  4. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas Chemical Formulas and Moles Until now, when you needed to perform molar conversions, you were given the molar mass of compounds in a sample. Where does this molar mass of compounds come from? You can determine the molar mass of compounds the same way that you find the molar mass of individual elements by using the periodic table. Formulas Express Composition You have learned that covalent compounds, such as water and hexachloroethane, consist of molecules as units. Formulas for covalent compounds show both the elements and the number of atoms of each element in a molecule. Hexachloroethane has the formula C2Cl6. Each molecule has 8 atoms covalently bonded to each other. Ionic compounds aren’t found as molecules, so their formulas do not show numbers of atoms. Instead, the formula shows the simplest ratio of cations and anions.

  5. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas Formulas Are Used to Calculate Molar Masses A formula tells you what atoms (or ions) are present in an element or compound. So, from a formula you can find the mass of a mole of the substance, or its molar mass. To do this you use the formula to tell you how many of which Atoms an to look up there mass from the periodic table. Find the molar mass for each of the following compounds: a. CsI b. C12H22O11 c. HC2H3O2 d. CaHPO4 e. I2 f. Mg3(PO4)2 259.8 g/mol 342.0 g/mol 60.0 g/mol 136.1 g/mol 253.8 g/mol 262.9 g/mol

  6. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

  7. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

  8. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

  9. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

  10. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

  11. Chapter 7 – The Mole and Chemical Composition Sec 2 - Relative Atomic Mass and Chemical Formulas

More Related