Chapter 6
Post Lab 6.4 to the end
2009
Synthesis of Zinc Chloride
(single-replacement)
A + B → AB
Zn + 2HCl → ZnCl2 + H2
By Amparo Krug 2009
Group Data
A.
B.
C.
D.
Zn metal initial _________ g
Zn metal final __________ g
Empty dish __________ g
Dish with solid (ZnCl) ________ g
Total 38 points on grade book divide by 2, 19 points
Calculations
• Mass of Zinc Reacted = B – A
• Mass of ZnCl produced = D – C
• Ratio of mass of Zn reacted
= ____
mass of ZnCl produced
Class Data example
Zn reacted (g)
ZnCl produced (g)
0.43
0.77
0.86
1.11
1.3
2.53
1.71
3.54
1.9
1.48
1.9
3.97
1.88
3.98
1.8
3.71
0.42
0.83
0.87
1.75
Ratio (Zn reacted/ZnCl produced
Graph
• ZnCl produced vs. Zn reacted.
Dependent
Variable
Independent Variable
• BDQ1 What is the gas given off in the
reaction? The gas is hydrogen
• BDQ2 Why should you add the
washing water to the evaporating dish?
Because it contains some of the
dissolved product
• BDQ3 How much of the metal reacted
with the HCl? Mass Zn initial – mass of
Zn remaining.
• BDQ4 What is the ratio of the mass of zinc
reacted to the mass of zinc chloride formed?
0.48
• BDQ5 Compare your results with those of
your classmates. Did an excess of either
zinc or hydrochloric acid affect your results?
No an excess of either reactant did not affect
the final ration.
• BDQ6 If the zinc chloride were not
completely dry when massed, how would
this affect your ratio? The mass of the
product would be larger and the final ratio
would therefore be smaller.
Graph
Best Fit Line
Zn reacted vs ZnCl produced
ZnCl produced (g)
5
4
3
ZnCl produced
2
1
0
0
0.5
1
1.5
Zn reacted (g)
2
2.5
Conclusion
Purpose
The purpose of this experiment is to investigate what
happens when a metal is dissolved in an acid.
Hypothesis
My hypothesis that the amount of Zinc that reacts with HCl
will depend on the amount of Zn was partly supported.
Group Data
Our group data revealed that the mass ratio of Zn reacted
to ZnCl produced was 0.50. See group data in page 35.
Class Data
The class also had an average mass ratio of 0.50. See the
group data in page 36.
Summary
Zinc and HCl will chemically combine in a constant
proportion no matter the amounts of the reactants that is
used.
• The graph shows a line with a positive slope which
flattens at about 4.0 g of ZnCl produced and1.9g Zn
reacted.
• There was enough HCl to react with 1.9g of ZnCl.
Any additional Zn would go un-reacted because
there is not enough HCl to react with.
Zn
Zn
Zn
Zn
HCl
HCl
Groups with less than 1.9g
of Zn did not have enough
Zn to react with the
Chlorine
HCl
HCl
The limiting reactant in
this part of the graph was
Zinc.
HCl
HCl
Left over HCl
Zn
HCl
Zn
HCl
Zn
Zn
HCl
HCl
Zn
Left over Zn
Zn
Groups with greater
than 1.9g Zn used up all
their HCl and were
evaporating water.
The limiting reactant in
these groups was HCl.
Lab 6.6 Reaction with
Copper
By Amparo
Krug
2006
POST LAB
This lab will be done as a demo
because we are running out of
time.
BDQ
BDQ 6.6.1:Does a reaction take place? Yes,
because there was a color change.
BDQ 6.6.2:Did the crucible and contents gain or
lose mass? Gained mass
• BDQ 6.6.3: Is your answer to the previous
question evidence that a reaction has taken
place? Increase in mass is evidence that
something was added to the copper.
• BDQ 6.6.4: What do you predict will
happen if you continue to heat the crucible
for an additional 10-15 minutes? Accept any
reasonable response.
• BDQ 6.6.5:
Do you think that all the copper has
reacted? No, because there were flakes of copper in
the solid. If not, what fraction do you estimate did
not react? about 1/8 (accept any reasonable
fraction)
• BDQ 6.7.1:
What does the remaining solid look
like? The solid remaining in test tube A looked like
copper.
• BDQ 6.7.2: Is the black substance a mixture? Yes,
because we were able to separated the unreacted
copper by using solubility.
• BDQ 6.9.1:
Can you identify the solid? It looks
like copper.
Conclusion (each purpose is address in one
encompassing statement)
• The purpose of these labs was to determine if:
• 6.6) The reaction of copper with oxygen goes to completion.
Our lab group found that the reaction of copper with oxygen
is incomplete producing a mixture.
• 6.7) Can this mixture be separated and the un-reacted copper
collected. Yes, we separated the un-reacted copper in the
mixture.
• 6.9) Can the Cu in the reacted CuO be isolated from the
compound. Definitely, we precipitated the copper that was
chemically combined with oxygen to make CuO.
• Theoretically, the mass of the copper in the two separations
of the product equals the initial mass of the Copper used.
Lab 6.6
• 2Cu (s) + O2 (g) > CuO +Cu
• A reaction has taken place because of the mass
increase (something is added to the Cu) and color
changed.
• CuO +Cu was a mixture and mixtures can be
separated by physical means. Which method was
used? Separation by solubility, dissolving
• CuO will dissolve in HCl and Cu will not
Lab 6.7
• CuO +Cu + 2HCl > 2CuCl + H2O
↓
Un-reacted Copper stays behind in test tube A
CuCl (green liquid) is now in test tube B
• Even though, copper reacted with air to
produce a compound, subjected to heat and
acid, we still were able to recover the copper.
The properties of the copper had not
changed.
• A substance that can keep its identity
through all these processes can be called an
Element.
Lab 6.9
• 2CuCl (green) + Zn + H2O > ZnCl2 (dissolves in water and
becomes clear) + 2Cu + H2O
↓
Copper is filtered out
• You know that a reaction has taken place because
of the color change, formation of precipitate, and
release of energy (exothermic). The product has a
different identity than the reactant.
Mixture
• Is a combination of different substances that
can be separated because they have different
physical properties – such as boiling point,
melting point, density.
• The substances are not chemically
bonded.
Concept Map
Concept
map
Mixture
Separate into
Pure substance
Pure substance
Can be
Can be
Compound
or
Broken into
Pure substance
Compound
Element
Element
Element
• Mixtures can be separated by
physical means into pure
substance.
• A pure substance can be a
compound or an element
Compounds
1. Cannot be separated by physical means, because
they are chemically bonded.
2. Have different properties from the elements of
which they are made.
3. Are synthesize from other pure substances in
constant ( definite ) proportions.
4. Can be written as a chemical formula which shows
the proportion of the elements in the compound.
Elements:
• Are pure substances made up of atoms
of
the same type, all with the same atomic
number.
• Cannot be broken down by
electrolysis, reacting with acid, nor heating to
form simpler substances.
In summary
• Compounds can be separated into other
compounds or elements
• But Elements cannot be subdivided.
• Famous Scientist who helped separated
compounds into elements.
ANTOINE LAURENT LAVOISIER, 1743-1794
• Discovered iron, copper, silver,
gold, hydrogen,
oxygen, and carbon.
• Discovered the true nature of
burning
– Chemical addition of oxygen
• Introduced quantitative analysis
• Help invent the metric system
• Father of modern chemistry
Alessandro Volta
• invents the battery,
1800, which helped
chemist separate
pure substances into
other pure
substances
(elements and
compounds)
Sir Humphry Davy, 1778 – 1829
• English chemist using electrolysis
decomposes Potash into
potassium and sodium in 1807.
• Isolates calcium from Lime (as in
limestone)in 1808.
• Isolates strontium, barium and
magnesium in 1808.
• Davy isolates the new gas from his
experiments with muriatic acid
and names it chlorine because
of its’ green color.
• Discovered the anesthetic action
of nitrous oxide.
Elements Near the Surface of the Earth
(top 8)
1.
2.
3.
4.
5.
6.
7.
8.
Oxygen
Silicon
Hydrogen
Aluminum
Iron
Calcium
Sodium
Magnesium
• The first 5 form 92% of the total
mass of the elements found near
the surface of the earth.
Silicates
• Oxygen and silicon form silicon dioxide.
• Silicon dioxide is the compound found in rock
forming minerals.
Ores are materials found in the ground from which
metals can be profitably extracted.
• Iron is produced by
mixing iron ore with
coal or charcoal and
heated strongly
• Aluminum comes from
Bauxite –aluminum ore