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Chapter 07: Chemical Quantities

Chapter 07: Chemical Quantities. Chemistry I A ALPHA Academy. Amedeo Avogadro: (1776 - 1856), Born in Turin, Italy. Amedeo Avogadro gets credit for our term “The Mole” Read an interview with Avagadro He wrote a now classic paper where the mole concept has it’s beginnings in gas volumes.

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Chapter 07: Chemical Quantities

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  1. Chapter 07: Chemical Quantities Chemistry I A ALPHA Academy

  2. Amedeo Avogadro: (1776 - 1856), Born in Turin, Italy • Amedeo Avogadro gets credit for our term “The Mole” • Read an interview with Avagadro • He wrote a now classic paper where the mole concept has it’s beginnings in gas volumes. http://www.chemheritage.org/EducationalServices/chemach/ppt/aa.html

  3. Counting Matter What are some everyday ways we count matter? 1. 2. 3. DOZEN = 12 things 1 GROSS = 144 things What about molecules? Or atoms? BUSHEL of corn = 21.772 kg 1 MOLE = 6.02 x 1023 things

  4. The Mole • It represents a counted number of things. • IN Chemistry the term MOLE represents the number of particles in a substance. In Chemistry is NOT this furry little animal or the spot on your face…

  5. Just how many is a mole? • One mole represents 6.02 x 1023 of things. This is called Avogadro’s number. • One mole of most elements contains 6.02 x 1023 atoms. • However, some elements naturally exist as diatomic molecules (the “magic 7”) • These contain Avogadro’s number of molecules

  6. Just how big is a mole? • Listen to The Mole Song! • An Avogadro's number of standard soft drink cans would cover the surface of the earth to a depth of over 200 miles • If you had Avogadro's number of un-popped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles.

  7. Just how big is a mole? • If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole. • Don’t forget to draw your number and get your “Take Home” Mole Activity Project!

  8. Molar Mass • Defn: is the mass (think grams) of one mole of a substance • Atomic masses of atoms are relative masses based on the mass of carbon-12 • To calculate the molar mass of a compound, you add up the molar masses of all the elements in that compound

  9. Molar Mass Practice • What is the mass of 1.00 mole of Carbon? Of Nitrogen? • Find the molar mass for: • SO3 • Na2SO4 1 mole C = 12.0 grams 1 mole N = 14.0 grams SO3= 80 g/mole 1 Mole = 142.043g Tutorial Site Molar Mass Calculator for homework help

  10. Molar Mass Practice • When you see 1.00 mole = _?_ g, think “g means GO to the PERIODIC TABLE” to find the molar mass. Do the worksheets: Gram Formula Mass and Molar Mass before you continue! http://www.webelements.com/

  11. Solving the Problems Samples Required: dimensional analysis/factor label • How many molecules are in 3.00 moles of N2? • How many moles of Na are in 1.10 x 1023 atoms?

  12. Grams-Mole Conversions • How many moles are in 56.8 g of HCl? • How many grams are in .05 moles Na2SO4? Now try the worksheets on Gram/Mole conversions. Get help from your teacher!

  13. Molar Volume • The volume of a gas is usually measured at standard temperature and pressure (_STP_) • Standard temp = ___0°_ C • Standard pressure = ___1___ atmosphere (atm) • 1 mole of any gas occupies __22.4__ L of space at STP

  14. Molar Volume Practice • How many moles would 45.0 L of He gas be? • How many liters of O2 would 3.8 moles occupy? Now Do the Moles of Gases worksheet

  15. Putting it all together • 1.0 mole = _6.02 x 1023___atoms or molecules = _?__ g = _22.4 L (at STP)

  16. Helpful Chart! MOLES Grams Volume in Liters Atoms or Molecules

  17. Percent Composition • the percentage by mass of each element in a compound • The percent comp. is found by using the following formula:

  18. % Composition Practice • What is the percent of C & H in C2H6? • What is the percent of each element in Na2SO3?

  19. Bonus: Empirical Formulas • This is the LOWEST whole number ratio of the elements in a compound. For example, the empirical formula for C6H6 is CH • What is the empirical formula for each? • C2H6 • C6H12O6

  20. BONUS: Calculating Empirical Formula • To _calculate__ the empirical formula, given the mass or percent of elements in compound, follow these steps: • If given a percent sign, remove the sign & change to _grams_. You are assuming you have 100 g of the compound. • Convert the grams to _moles__. • Decide which number of moles is the lowest_, then divide each number of moles by this number. • If the number divides out evenly, these are the subscripts of the elements in the compound. If any of the numbers have a .5, _multiply them all by two & then place these numbers as the subscripts.

  21. Sample Problems • What is the empirical formula for a compound which is 75 % C and 25 % H? • What is the empirical formula for a compound which has • 48.64 % C, • 8.16 % H • 43.20 % O

  22. Sample Problems #2 • What is the empirical formula of • 40.68 % C • 5.08 % H • 54.24 % O

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