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. http://www.chemheritage.org/EducationalServices/chemach/ppt/aa.html

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

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…

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

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.

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!

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

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

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/

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?

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!

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

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

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

Helpful Chart! MOLES Grams Volume in Liters Atoms or Molecules

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

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

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

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.

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

Sample Problems #2 What is the empirical formula of 40.68 % C 5.08 % H