st.patrick regional sec
chemistry 11, block a
chemistry 11, block a
Sunday, November 1, 2009 3:39 PM
Atoms and MoleculesFor monoatomic elements
a molecule = an element
(Ne) = (Ne)
Diatomic elements:
Molecule = Element
Cl2 = Cl
Molecules of compounds
H--H
|O|
Molecule
2 'H' atoms in 1 molecule
1 'O' atom in 1 molecule
Example: Write Ammonium Carbonate
Answer: (NH4)2CO3
N: 2
H: 8
O: 3
C: 1
Moles<>Molecules
6.02 x 10^23 molecules/ 1 mol or 1 mol/ 6.02 x 10^23 molecules
Example: How many molecules are in 0.25 mol of CO2
Answer: 0.25 mol x 6.02 x 10^23 molec/1 mol = 1.505 x 10^23 molec.
Example: 5.1772 x 10^24 molecules of H2O = ? moles
Answer: 5.1772 x 10^24 molec x 1 mol/ 6.02 x 10^23 molec = 8.6 mol
Example: Find the number of 'H' atoms in 4.0 mol of ammonia? [moles->molecules-> H atoms]
4.0 mol =x3 molecules
Answer: 4.0 mol x 6.02 x 10^23/ 1 mol = 2.41 x 10 ^24 molecules x3 = 7.22 x 10^24 'H' atoms
