# Chemical Quantities Chapter 6. Atomic Structure Review Atomic Mass –Weighted average of all known isotopes of an element Formula Mass –The sum of the.

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Chemical Quantities Chapter 6

Atomic Structure Review Atomic Mass –Weighted average of all known isotopes of an element Formula Mass –The sum of the atomic masses of all the elements in a compound –Stated in amu’s

Calculating the Formula Mass 3 Steps to calculate the formula mass Above all Double Check to make sure you have the correct formula 1.Count the atoms of each element 2.Multiply the number of atoms by the elements atomic mass (round mass to hundredths) 3.Add all the masses together

B. Molar Mass Examples carbon aluminum zinc 12.01 g/mol 26.98 g/mol 65.39 g/mol

B. Molar Mass Examples water sodium chloride –H2O–H2O –2(1.01) + 16.00 = 18.02 g/mol –NaCl –22.99 + 35.45 = 58.44 g/mol

B. Molar Mass Examples sodium bicarbonate sucrose –NaHCO 3 –22.99 + 1.01 + 12.01 + 3(16.00) = 84.01 g/mol –C 12 H 22 O 11 –12(12.01) + 22(1.01) + 11(16.00) = 342.34 g/mol

The Mole, Chemistry's Mascot

Mole Allegiance (Background: When saying the pledge of allegiance to the U.S. flag, one faces the flag. If no flag is present, one should face our nation's capitol, Washington D.C. When saying the pledge to the mole, a real mole is usually not present. So, one should bend over and face the earth!)

Mole Allegiance I pledge allegiance to the mole, and to the science from which it comes, one SI unit, extremely divisible, with micromoles and millimoles for all. –(Provided by R. Thomas Myers - Kent State University, Kent, OH) I pledge allegiance to the mole, to the International Union of Pure and Applied Chemistry, and to the atomic mass for which it stands, one number, most divisible, with atoms and molecules for all. – (Provided by Sylvia Cooper - Morgantown High School, Morgantown, WV)

Units of Measurement Fundamental Units –Dozen = 12 things –Decade = 10 years –Gross = 144 things –Ream = 100 things –I Mole = 6.02 x 10 23

Measuring with Moles The Mole is a counting unit –Called the chemist’s dozen –Used to count number of Atoms Molecules (nm + nm) or (m + nm) –We will count both atoms and molecules

Conversions with Moles Given x Conversion = Unknown Factor Factor Label Method

Conversions with Moles How do you find mass of one mole of substance? We can do this if we know the formula mass When we do this we get the MOLAR MASS –The mass in grams of 1 mole of substance is equal to the formula mass –Units: grams/mol

Board Examples

Super Mole Highway So Far we Can Convert Between –Moles –Grams –Particles The Mole Highway will help us convert from one to another

Super Mole Highway molar mass (g/mol) MASS IN GRAMS MOLES NUMBER OF PARTICLES 6.02  10 23 (particles/mol)

Volume and Moles How Do You Measure the Amount of Gas Particles in a Substance –Use STP (Standard Temp and Pressure = 20 0 C and 1 atm) –We use STP because gas volumes vary with temperature –Key Points One mole of gas at STP will occupy a volume of 22.4L 22.4L of any gas will contain 6.02 x 10 23 representative particles

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