University:
Glendale Community College
Course:
CHM130 | Fundamental Chemistry
Academic year:

2021
Views:

434

Pages:

3
Author:

nvcheekz0904ps

8.1 Avogadro’s Number and the Mole Chapter 8: The Mole Concept Eggs come in dozens 12 eggs = 1 dozen Atoms come in moles 6.02 x 1023 atoms = 1 mole = NA NA is a ginormous number! How big is it? One mole of softballs would be the size of the Earth! Mole Examples The Mole  Atoms are so tiny that one mole of atoms is sugar about a handful.  The mass of a mole of atoms = the atomic mass in grams on the Periodic Table.  1 mole of C atoms is 12.01 grams  1 mole of Na atoms is 22.99 grams  What is the mass of one mole of Ne atoms? water lead mercury copper sulfur sodium chloride 8.2 Mole Calculations I: Avogadro’s Number 6.02 x 1023 atoms or mlcls or 1 mol 1 mol 6.02 x 1023atoms or mlcls 1. How many calcium atoms are in 0.250 moles of calcium? 2. Calculate the moles of 3.75 x gas? 1027 molecules of oxygen 8.3 Molar Mass Molar mass tells us how much mass is in one mole of substance. Periodic Table masses are in units of (g/mol). Very important – the units are grams per 1 mole, not just grams How many grams in one mole of:  carbon?  gold?  sodium? What do they all have in common? 1 Molar Mass Calculate the molar mass of barium hydroxide. 1.What is the formula? 8.4 Grams to Moles (Mole Calcs II)  Use Molar Mass as (g/mol) or (mol/g)  How many grams is 1.667 moles of oxygen gas? 2.Add up the mass for every atom.  How many moles is 45 grams of silver?  How many grams is 0.0554 moles of water?  8.5 Molar Volume Volume of 1 mole of gas Molar Volume  Gases are mostly empty space so they ALL have the same volume despite different mass.  22.4 L per 1 mole of any gas at STP  22.4 L / mol or 1 mol / 22.4 L  STP = Standard Temperature and Pressure  0oC and 1 atm Molar Volume What is the volume of 1.25 moles of gas at STP? What is the mass of 4.50 L of chlorine gas at STP? Density of Gases Density = mass / volume For gases, we use units of g/L. Calculate the density of ammonia gas, NH3, at STP. 2 Mole Conversion Chart Practice Example  How many grams does 17.35 liters of neon gas weigh at STP? How many atoms is this? 8.7 Percent Composition  Percent by mass (of each element in a compound)  Divide the total element molar mass by the total compound molar mass. Percent Composition Practice  Find the percent composition for TNT, C7H5(NO2)3.  Total molar mass is 227.15 grams per mole  % = (element / compound) x 100  What is the percent composition of water?  Note the %’s should add up to 100% total Chapter 8 Practice  How many liters will 3.425 grams of carbon dioxide gas occupy at STP? Ch. 8 Self-Test, p. 248  Try 1-7, 10-13  Answers in Appendix J  How many molecules are in 3.425 grams of carbon dioxide?  What will be the mass of 3.0 x 1015 molecules of carbon dioxide? 3