Solids
• Solids are formed when temperatures
are low enough to prevent molecules
from moving around their neighbors
• Molecules or atoms in solids
vibrate/oscillate around a fixed position
– All the atoms in a solid essentially move in
unison
Types of Solids
•
Two major classifications: Crystalline and
Amorphous
1. Crystalline Solids: All atoms, ions or
molecules in the solid lie in an orderly array.
Long range order exists within a crystalline
solid
2. Amorphous Solids: The atoms, ions or
molecules in an amorphous solid lie in a
seemingly random arrangement.
•
•
Amorphous solids look like we took a snapshot
of a liquid
Glass is an amorphous solid
Crystalline Solids
1. Molecular Solids: Assemblies of discrete
molecules held together by intermolecular
forces (eg: Quartz)
2. Network Solids: Atoms are covalently
bonded to their neighbors throughout the
extent of the solid (eg: Diamonds)
3. Metallic Solids: Metal cations held together
by a sea of electrons
4. Ionic Solids: Built from the mutual attraction
of anions and cations
Fundamentals Section L:
Reaction Stoichiometry
N2 (g) + 3H2 (g) --> 2NH3 (g)
This tells us that 1 mole of N2 will react with 3
moles of H2 to form 2 moles of NH3
We can also relate reactants and products to
each other by stoichiometric relations
For the ammonia forming reaction:
1 mole of N2 is chemically equivalent to 3 moles of H2
1 mole of N2 is chemically equivalent to 2 moles of NH3
3 moles of H2 is chemically equivalent to 2 moles of NH3
Using Stoichiometric Relations
• We can use them to predict/calculate
amounts of materials reacted or
products formed
• Take the fuel cell example:
2H2(g) + O2(g) --> 2H2O(l)
How much water would be made from
0.25 moles of O2 reacting with H2?
• Looking at the chemical equation, we can see
that:
1 mole of O2 is chemically equivalent to 2 moles of H2O
We can set up a conversion factor based upon this
relationship for use in calculations:
2 moles H 2O
1 mole of O 2
Now we can use the stoichiometric relationship:



Calculate the mass of potassium metal needed to
react with 0.450 g of hydrogen gas to produce solid
potassium hydride.
Step 1: Balanced chemical reaction
Step 2: Take what you’re given and convert it to moles
Step 3: Use the stoichiometric coefficients to convert
moles of one substance to moles of another
Step 4: Convert Moles to Mass
Potassium superoxide, KO2, is utilized in a closed system
breathing apparatus to remove carbon dioxide and water
from exhaled air. The removal of water generates
oxygen for breathing by the reaction:
4KO2(s) + 2H2O(l) --> 3O2(g) + 4KOH(s)
Potassium hydroxide removes carbon dioxide from the
apparatus by the reaction:
KOH(s) +CO2(g) --> KHCO3(g)
a) What mass of potassium superoxide generates 115g of
O 2?
b) What mass of CO2 can be removed from the apparatus
by 75.0 g of KO2?