CHEMISTRY IN CONTEXT
LAB 10: BINARY COMPOUNDS, PAGE 1
CYCLE 5
NAME
Binary Compound Reactions
Understanding Binary Compound Formula Writing & Chemical Names
PRE-LAB DISCUSSION:
Recall from lecture that formula writing is based on the oxidation number of an element.
Elements that will form positive ions, mostly metals, are called cations. Examples of cations are
all of the alkali metals (like K1+), alkaline earth metals (like Mg2+), and most of the transition
metals (like Zn2+). Elements that will form negative ions are called anions. Examples of anions
are the halogens (like Cl1-) and other non-metals (like N3-). When a cation and anion come
together, a compound is formed. A compound is chemical combination of elements using the
electrons shared or exchanged between them to form a chemically bonded substance.
Whether an element will be a cation or anion (its oxidation
number) will be determined by the valence number of that
element. Looking at your periodic table, there are some
transition metals that can have several different valence
numbers. So, how do you determine their oxidation state?
Essentially, you must KNOW what type of that element you
have. For this reason, when scientists know, for example, that
cobalt is behaving with an oxidation state of +2, they will put
a (II) after the element name. So, the substance CoCl2 would
be named cobalt (II) chloride. Many elements in the
transition metals can behave in a fashion where they could have a different oxidation state from
what is expected. Copper is another example. In the form that we will use it today, it will
actually have a +2 oxidation state instead of its expect +1. If you recall in the flame tests lab,
two different solutions of copper had two different colors (green or blue). This was due to their
different oxidation states. So, we will write the name of the substance we will be using today as
copper (II) chloride. Whenever you see the roman numeral in parentheses after the element
name, this valence number takes precedent over the expected number in the Periodic Table.
Some important safety reminders:
1)
You will observe STANDARD PRECAUTIONS today. This includes goggles
and lab coat during the ENTIRE LAB. Points will be deducted from your lab
grade if Mr. Adams observes you WITHOUT these items on.
2)
Both substances used today are relatively innocuous (non-hazardous), however,
the copper (II) chloride and copper sulfate may stain clothing and should be
washed off your hands if you come into contact with it.
3)
You will be observing a demo with the combustion of magnesium metal to
chemically combine magnesium and oxygen. Magnesium burns with a VERY
bright flame. It should NOT be looked at directly and ONLY out the corner of
one’s eye to avoid eye damage.
CHEMISTRY IN CONTEXT
LAB 10: BINARY COMPOUNDS, PAGE 2
CYCLE 5
NAME
APPARATUS/MATERIALS:
magnesium ribbon (teacher, ONLY)
open flame (teacher, ONLY)
crucible tongs (teacher, ONLY)
copper (II) chloride
aluminum square
600mL beaker
large glass stirring rod
digital balance with massing dishes
copper sulfate solution
plastic pipette
iron filings
2 medium sized test tubes
test tube rack
PROCEDURE:
1)
Observe as your teacher demonstrates how magnesium metal combines with oxygen.
After viewing the demonstration, fill in the row (a) line in Data Table #1 in your
Analysis section. The remainder of the rows will be filled in as you proceed with the
remainder of the experiment.
2)
Use one of the plastic massing dishes to measure out approximately 2 grams of iron
filings. Take the plastic massing dish with the iron filings back to your lab station.
3)
Acquire a plastic pipette and use it to measure out approximately 2mL of copper
sulfate solution into a medium-sized test tube. Place the test tube into your test tube
rack while you complete procedure step #4.
4)
At the sink, rinse out your second empty medium-sized test tube. DO NOT dry it.
Make sure to get the entire inside wet.
5)
Squeeze your plastic massing dish by opposite corners to create a folder in the dish
so that you can easily pour it into the wet, washed test tube. Turn the test tube as you
add the iron filings into the test tube so that you coat the top third of the test tube ON
THE INSIDE with iron filings. Be CAREFUL not to spill the filings!
6)
Once you have added the iron filings. Carefully tap the bottom of the iron filing test
tube on the bottom of your hand to scatter some of the filings to the bottom. What
color do the iron filings appear? Record this observation in the Observation Table in
the Data/Observations section. What color does the copper sulfate solution appear?
Record this observation in the Observation Table in the Data/Observations section.
7)
Use your pipette to carefully add one BIG pipette squeeze of copper sulfate solution
to the iron filings test tube by holding the iron filings test tube sideways and allowing
the solution to come into contact with the filings as it washes down the inside of your
test tube. Note the IMMEDIATE reaction that occurs. Do you feel heat on the test
tube? How do the colors change? Record your observations in the Observation Table
in the Data/Observations section.
CHEMISTRY IN CONTEXT
LAB 10: BINARY COMPOUNDS, PAGE 3
CYCLE 5
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NAME
After you have made your observations and finished Step #7, rinse your test tube
into the Erlenmeyer flasks in the sinks.
Wipe out your massing pan with a DRY paper towel and throw the paper towel
away.
Use the digital balance and the scoopula/spatula at the main lab bench to acquire to
10 grams of copper chloride.
Add the copper chloride to a 600mL beaker with 300mL of water. Use the large
stirring rod to mix your solution thoroughly to dissolve MOST of the crystals and turn
the solution a light “sky” blue.
Acquire a square of aluminum foil and fashion a small boat to be able to sit in the
top of your beaker but DON’T put it into the beaker yet.
Make notes in the Observation Table in the Data/Observations section how the
copper chloride solution and aluminum foil appear.
Then, place your aluminum boat into the copper chloride solution. Allow it to float
for a moment and observe any reaction. If a reaction has NOT occurred in about two
minutes, subject the small defenseless boat to a hurricane and mix your solution with
the stirrer. Be careful not to spill! Note how the copper chloride solution changes
and how the aluminum boat changes in the Observation Table in the
Data/Observations section in your Data/Observation section.
Dispose of this waste in the Erlenmeyer flask in the sink.
Clean ALL glassware and return your pipettes and massing dishes to the main lab
bench.
Fill in the remaining sections of the table in your Analysis section by following the
DATA/OBSERVATIONS:
APPEARANCE
BEFORE
iron filings
copper sulfate
aluminum
copper chloride
APPEARANCE
AFTER
CHEMISTRY IN CONTEXT
LAB 10: BINARY COMPOUNDS, PAGE 4
CYCLE 5
NAME
ANALYSIS:
1)
Use your Periodic Tables to fill in this table:
METAL'S
SYMBOL
NONMETAL'S
SYMBOL
(with oxidation
number)
(with oxidation
number)
CHEMICAL
FORMULA
COMPOUND
NAME
a)
b)
copper (I) sulfate
c)
iron (III) sulfate
d)
copper (II) chloride
e)
aluminum chloride
2)
Rust and tarnish is a metal combining with oxygen. Write formula and compound names
for following rusts/tarnishes:
Formula
Name
a)
silver tarnish
b)
gold rust
c)
aluminum rust