1 / 16

Chemistry Unit 7: Moles

Chemistry Unit 7: Moles. C8A- I will define & use the concept of a mole. C8B – I will use the mole concept to calculate the number of atoms, ions, or molecules in a sample of material. C8C – I will calculate percent composition & empirical and molecular formulas. VERY.

maitland
Download Presentation

Chemistry Unit 7: Moles

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. Chemistry Unit 7: Moles C8A- I will define & use the concept of a mole.C8B – I will use the mole concept to calculate the number of atoms, ions, or molecules in a sample of material.C8C – I will calculate percent composition & empirical and molecular formulas. created by C. Johannesson modified by T. Howard

  2. VERY A large amount!!!! • A. mole – amount of substance that has particles equal to the number of atoms in 12g of carbon 12 OR the amount of substance that has Avogadro’s # of particles --- 6.02 x 1023 particles

  3. A. What is the Mole? HOW LARGE IS IT??? 1 mole of pennies would cover the Earth 1/4 mile deep! 1 mole of hockey pucks would equal the mass of the moon! 1 mole of basketballs would fill a bag the size of the earth!

  4. B. Avogadro’s number – number of particles in 1 mole of a pure substance 6.02 x 1023

  5. C. atomic mass number – number of protons + neutrons; measured in amu’s ---this is NOT on the p-table D. average atomic mass number – average weighted mass of an atom/element ---this is on the periodic table If you change the units from amu to grams you now have the amount of grams in 1 mole of the element – something you can actually measure on a scale!

  6. avg atomic mass calculation ( % isotope #1) ( mass isotope #1) + ( % iso#2) ( mass iso#2) +… 100 C6D Use isotopic composition to calculate average atomic mass of an element.

  7. The natural abundance for boron isotopes is: 19.9% 10B (10 amu) and 80.1% 11B (11amu). Calculate the atomic weight of boron. [(19.9 × 10) + (80.1 × 11)] 100 avg atomic mass is 10.801 amu

  8. E. Molar mass – mass of 1 mole of a pure substance----units are grams/mole or g/mol • Turn to p.7 in your packet (Molar Mass Wkst 3)! • Look at right side of page & we will do a couple of examples…the rest is for you to complete

  9. 1. Molar mass is “equal” to the mass # of an element in amu’s, so if an element has an mass # of 39.0983 amu’s then the molar mass is 39.0983 g/mol you just change the unit of measurement!

  10. F. formula mass aka formula weight– sum of all the mass numbers of the atoms in a compound • the term formula mass is usually associated with ionic compounds & • the term molecular mass is usually associated with covalent compounds • they’re the same basic thing

  11. from the periodic table • #3 – BeCl2 Be = 1 x 9.012 g = 9.012 g Cl = 2 x 35.453 g = + 70.906 g 79.918 g number of atoms in the formula formula mass of BeCl2 aka molar mass

  12. #7 – Mg(OH)2 Mg = 1 x 24.305 = 24.305 g O = 2 x 15.999 = 31.998 g H = 2 x 1.008 = 2.016 g f.m. of Mg(OH)2 = 58.319 g You need to do the rest on your own!

  13. G. percent composition- percent by mass of each element in a compound mass of element x 100 = % element in cmpd mass of total cmpd

  14. What percent by mass of Mg(OH)2 is oxygen? • find the formula mass of the Mg(OH)2 Mg = 1 x 24.305 = 24.305 g O = 2 x 15.999 = 31.998 g H = 2 x 1.008 = 2.016 g f.m. of Mg(OH)2 = 58.319 g

  15. mass of element x 100 = % element in cmpd mass of total cmpd 31.998g O x 100 = 54.87% oxygen by mass 58.319g Mg(OH)2 That means more than half of the mass of the Mg(OH)2 (what is the name of the compound?) is due to oxygen!

  16. H. % error= (observed value - actual value) x 100 actual value Observed value refers to the data you got in the lab while actual value is the “correct” or “book” value/answer.

More Related