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AP Chapter 3 - Atomic Mass Atoms are so small it is...

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1 Atomic Mass circle6 Atoms are so small, it is difficult to discuss how much they weigh in grams circle6 Use atomic mass units. circle6 an atomic mass unit (amu) is one twelfth the mass of a carbon-12 atom circle6 This gives us a basis for comparison circle6 The decimal numbers on the table are atomic masses in amu They are not whole numbers circle6 Because they are based on averages of atoms and of isotopes. circle6 can figure out the average atomic mass from the mass of the isotopes and their relative abundance. circle6 add up the percent as decimals times the masses of the isotopes. Examples circle6 There are two isotopes of carbon 12 C with a mass of 12.00000 amu(98.892%), and 13 C with a mass of 13.00335 amu (1.108%) circle6 There are two isotopes of nitrogen , one with an atomic mass of 14.0031 amu and one with a mass of 15.0001 amu. What is the percent abundance of each? The Mole circle6 The mole is a number circle6 a very large number, but still, just a number circle6 6.022 x 10 23 of anything is a mole circle6 a large dozen circle6 The number of atoms in exactly 12 grams of carbon-12 The Mole circle6 Makes the numbers on the table the mass of the average atom circle6 Average atomic mass circle6 Just atomic mass
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2 Molar mass circle6 mass of 1 mole of a substance circle6 often called molecular weight. circle6 To determine the molar mass of an element, look on the table. circle6 To determine the molar mass of a compound, add up the molar masses of the elements that make it up. Find the molar mass of circle6 CH 4 circle6 Mg 3 P 2 circle6 Ca(NO 3 ) 2 circle6 Al 2 (Cr 2 O 7 ) 3 circle6 CaSO 4 2H 2 O Percent Composition circle6 Percent of each element a compound is composed of.
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