Download Name __KEY____________ Per. ______ Polarity and

Name __KEY____________ Per. _________
Polarity and Stoichiometry Review
When examining trends in the periodic table, as we move towards the top-right the elements have a greater
_electronegativity_ (atomic radius/ electronegativity), which is a measure of how much they want to _ hold onto_
(hold onto/ let go of) their electrons. For any two elements that share a chemical bond, we can calculate the difference
in electronegativity by _subtracting_ (multiplying/ subtracting/ adding) their electronegativity values that we can get
from a table. In our textbook there is a table on page 177. As the difference in electronegativity becomes __larger__
(larger/ smaller) bonds will go from being nonpolar covalent to polar covalent to ionic.
If a bond is polar that means that the atoms share their electrons __ unevenly__ (unevenly / evenly), which
causes the more electronegative element to have a _ slightly_ (full/ slightly) negative charge and the other to have a
slightly _ positive_ (positive/ negative) charge. As the difference in electronegativity becomes greater substances will
also have __ higher__ (higher/ lower) melting points. This is evident in how the nonpolar covalent compound methane
is a ___ gas___ (gas/ liquid/ solid) at room temperature, the polar covalent compound water is a __ liquid__ (gas/
liquid/ solid) at room temperature, and the ionic compound sodium chloride is a __ solid__ (gas/ liquid/ solid) at room
temperature.
For chemical reactions the reactants are found on the ___ left___ (left/ right) side of the chemical equation and
the products are found on the __ right__ (left/ right) side of the chemical equation. Two quantities that are always
conserved, meaning stays the same, during a chemical reaction are [circle 2] (number and type of atoms/ number of
molecules/ mass/ volume/ temperature). There are 4 basic types of chemical reactions which are [list them]:
1. ____combination____ 2. ____ decomposition____ 3. ____ single substitution___ 4. ____double substitution___
One specific type of double substitution reaction is combustion where some type of hydrocarbon fuel reacts
with oxygen gas and burns. When there is sufficient oxygen present, ___ complete___ (complete/ incomplete)
combustion occurs and the products are carbon dioxide and water vapor. When there is not sufficient oxygen present,
____incomplete___ (complete/ incomplete) combustion occurs and the products are carbon monoxide and water
vapor. Carbon monoxide is an odorless, poisonous gas. Exposure to it leads to approximately 500 unintentional deaths
and 15,000 of emergency room visits each year in the United States. This is why you should never start a car inside a
garage while the garage door is closed and never operate a barbeque inside of a house.
Sometimes we want to use the amount of one reactant or product in a chemical reaction to predict the
maximum possible amount of another reactant or product. This is called _____stoichiometry_____ (density/ writing a
chemical formula/ stoichiometry).
Sometimes not all of both reactants are completely used up in a chemical reaction. The reactant that will be
completely used up is called the ___ limiting____ (limiting/ excess) reactant. The reactant that we have in extra
amounts of is called the ____ excess____ (limiting/ excess) reactant. When you divide the amount in moles of each
reactant by their coefficient from the balanced chemical equation, the lesser one is the limiting reactant.
Element
E.N.
Li
1.0
Na
1.0
K
0.9
C
2.5
N
3.0
O
3.5
F
4.0
S
2.5
Cl
3.0
Δ E.N. = | E.N.1 – E.N.2 |
Δ E.N. Range
0 to 0.5
0.5 to 1.9
1.9 or greater
Type of Bond*
Nonpolar Covalent
Polar Covalent
Ionic
1. Calculate Δ E.N. for each of the following bonds and state the type of bond.
a. C-Cl |2.5 – 3.0| = 0.5
(barely) polar covalent
b. F-Cl
|4.0 – 3.0| = 0.5
polar covalent
c. Li-F
|1.0 – 4.0| = 3.0
ionic
d. C-N
|2.5 – 3.0| = 0.5
(barely) polar covalent
e. C-O
|2.5 – 3.5| = 1.0
polar covalent
f.
|3.5 – 3.5| = 0
nonpolar covalent
O-O
2 B + 3 Cl2 2 BCl3
2) What is the mole ratio between boron (B) and chlorine gas (Cl2)?
2 mol B
1 mol Cl2
3) What is the mole ratio between boron (B) and boron trichloride (BCl3)?
2 mol B
2 mol BCl3
4) How many moles of chlorine gas (Cl2) are needed to completely react with 8 moles of boron (B)?
8 mol B
1
×
3 mol Cl2
2 mol B
= 12 mol Cl2
5) How many grams of boron trichloride (BCl3) are produced when 5.00 grams of boron (B) reacts completely with
chlorine gas (Cl2)?
Molar Mass of B: 10.8 g/mol
Molar Mass of BCl3:
from periodic table
B: 1 × 10.8 = 10.8
Cl: 3 × 35.5 = + 106.5
= 117.3 g/mol
5.00 g B
1
×
1 mol B
10.8 g B
×
117.3 g BCl3
2 mol BCl3
×
1 mol BCl3
2 mol B
= 54.3 g BCl3
1 FeCl3 + 3 NaOH 1 Fe(OH)3 + 3 NaCl
6) If you have 5 moles of iron (III) chloride (FeCl3) and 12 moles of sodium hydroxide (NaOH), which is the limiting
12 mol NaOH
5 mol FeCl3
reactant? Which is the excess reactant?
=5
4=
3
1
excess
limiting
7) How many moles of sodium chloride (NaCl) will be produced if the above amounts of the reactants react?
>
12 mol NaOH
×
1
3 mol NaCl
= 12 mol NaCl
3 mol NaOH