1 / 27

Honors Chemistry

Honors Chemistry. Section 7.3. A chemical formula indicates: the elements present in a compound the relative number of atoms or ions of each element present in a compound Chemical formulas also allow chemists to calculate a number of other characteristic values for a compound: formula mass

ave
Download Presentation

Honors Chemistry

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. Honors Chemistry Section 7.3

  2. A chemical formula indicates: • the elements present in a compound • the relative number of atoms or ions of each element present in a compound • Chemical formulas also allow chemists to calculate a number of other characteristic values for a compound: • formula mass • molar mass • percentage composition

  3. The formula massof any molecule, formula unit, or ion is the sum of the average atomic masses of all atoms represented in its formula. • example: formula mass of water, H2O average atomic mass of H: 1.01 amu average atomic mass of O: 16.00 Formula Masses

  4. Find the formula mass of Na2SO3 Problem

  5. The mass of a water molecule can be referred to as a molecular mass. • The mass of one formula unit of an ionic compound, such as NaCl, is not a molecular mass. • The mass of any unit represented by a chemical formula (H2O, NaCl) can be referred to as the formula mass. Formula Masses

  6. Video Formula Masses

  7. Find the formula mass of potassium chlorate, HClO3. Problem

  8. Video The Mole

  9. The molar mass of a substance is equal to the mass in grams of one mole, or 6.022 × 1023 particles, of the substance. • example: the molar mass of pure calcium, Ca, is 40.08 g/mol because one mole of calcium atoms has a mass of 40.08 g. • The molar mass of a compound is calculated by adding the masses of the elements present in a mole of the molecules or formula units that make up the compound. Molar Masses

  10. Calculating Molar Masses for Ionic Compounds

  11. What is the molar mass of barium nitrate, Ba(NO3)2? Problem

  12. How many moles of each atom are in one mole of K2SO4? • How many moles of each atom are in one mole of (NH4)2CrO4? Problem

  13. The molar mass of a compound can be used as a conversion factor to relate an amount in moles to a mass in grams for a given substance. • To convert moles to grams, multiply the amount in moles by the molar mass: Amount in moles × molar mass (g/mol) = mass in grams Molar Mass as a Conversion Factor

  14. SolvingMole Problems Condensed Version molar mass (grams) 1mole 1 mole 6.022 x 10^23 particles Grams Moles Particles Calculations (Atoms, molecules or formula units)

  15. Video Molar Mass as a Conversion Factor

  16. Calculate the molar mass of O2. • Use the molar mass of O2 to convert 2.50 moles to mass Problem

  17. What is the mass of 3.04 moles of NH3? Problem

  18. How many moles in 4.15 x 10-3 g of C6H12O6? Problem

  19. How many molecules are in this mass of C6H12O6? Problem

  20. It is often useful to know the percentage by mass of a particular element in a chemical compound. • To find the mass percentage of an element in a compound, the following equation can be used. • The mass percentage of an element in a compound is the same regardless of the sample’s size. Percentage Composition

  21. The percentage of an element in a compound can be calculated by determining how many grams of the element are present in one mole of the compound. • The percentage by mass of each element in a compound is known as the percentage compositionof the compound. Percentage Composition

  22. Some compounds have water molecules as part of their crystal structure. These substances are call hydrates. • Ex. – Na2SO4･10H2O • This water is included when calculating the molar mass. • You can drive this water off by careful heating. Water of Hydration

  23. What is the percentage of water in CaSO4·2H2O? Problem

  24. NH4NO3 is 35.0% N. How much N is in 49.0g of the compound? Problem

  25. Video Percentage Composition

  26. Percentage Composition Calculations

  27. Find the percentage composition of Ag2SO4. Problem

More Related