Exambusters Chemistry Study Cards 5

Atomic Mass
A weighted average mass of the atoms of an element; e.g. Atomic mass of Cl = 35.45, calculated from two isotopes: Cl-35, Cl-36
Molecular Mass

Found by adding all the atomic masses of an element. e.g. water, H2O: molecular mass = 18

Equation: 2(1) + 16 = 18 

6.02 X 1023 items; can be anything: atoms, elephants, marshmallows.
Avogadro’s Number
The number of atoms or formula units in x grams of an element or molecule, where x is the atomic or molecular mass. Always equal to 6.02 X 1023
How many molecules in 0.5 moles of CuNO2?
3.01 X 1023 molecules
How many grams in 5 moles of ammonia (NH3)?
85 grams
How many moles in 50 grams of Hydrogen gas (H2)?
25 moles

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