Tuesday, April 5, 2011
(SCH3U) Chemical Reactions Test
Name: ___________________________
Knowledge/Understanding – 20 Marks
Thinking/Investigation – 25 Marks
/60
Communication – 8 Marks
Application – 6 Marks
Section I – Multiple Choice (10 Marks – Knowledge/Understanding)
Choose the best answer for each of the following.
1. Which of the following would be the best example of a chemical change?
a. Burning toast
b. Melting water
c. Squeezing a sponge
d. Adding more sugar to a glass of water
e. Shaking salad dressing so that the oil and vinegar mix
2. Which of the following components are not necessary for every for every balanced
chemical equation?
a. Equal amounts of reactants and products
b. Proper chemical formulas
c. Coefficients in front of every compound
d. The states of every compound
e. Multiple products
3. When carbon dioxide is allowed to react with water, the resulting solution would be:
a. A salt
b. Neutral
c. Basic
d. Acidic
e. A very poor conductor of electricity
4. When magnesium oxide is allowed to react with water, the resulting solution would be:
a. A salt
b. Neutral
c. Basic
d. Acidic
e. A very poor conductor of electricity
5. Indicate which of the following compounds would not be soluble in water.
a. Sodium Acetate
b. Ferric Bromide
c. Ammonium Hydroxide
d. Potassium Sulfate
e. Lead II Carbonate
For the next five (5) questions, choose the correct name for the given reactions.
6.
€
K 2CO3(aq ) + CaCl2(s) ⎯
⎯→ 2KCl(aq ) + CaCO3(s)
a.
b.
c.
d.
e.
Synthesis
Decomposition
Combustion
Single Displacement
Double Displacement
⎯→ 2MgO(s)
7. 2Mg(s) + O2(g ) ⎯
€
a.
b.
c.
d.
e.
Synthesis
Decomposition
Combustion
Single Displacement
Double Displacement
⎯→ 2Al(s) + 3Cl2(g )
8. 2AlCl3(s) ⎯
€
a.
b.
c.
d.
e.
Synthesis
Decomposition
Combustion
Single Displacement
Double Displacement
⎯→ Li2CO3(s)
9. Li2O(s) + CO2(g ) ⎯
€
a.
b.
c.
d.
e.
Synthesis
Decomposition
Combustion
Single Displacement
Double Displacement
⎯→ 3K 2O(s) + 2Fe(s)
10. 6K(s) + Fe2O3(s) ⎯
€
a.
b.
c.
d.
e.
Synthesis
Decomposition
Combustion
Single Displacement
Double Displacement
Section II – Matching (10 Marks – K/U)
Match the term on the left with the appropriate definition on the right.
1
Product
A
2
Reactant
B
3
Water
C
4
Neutralization
D
5
Antoine Lavoisier
E
6
Hydrocarbon
F
7
Synthesis Reaction
G
8
Single Displacement
Reaction
Double Displacement
Reaction
Decomposition Reaction
H
9
10
I
J
K
L
This occurs when an equal amount of acid
solution is mixed with an equal amount of basic
solution
This type of reaction could involve the formation of
one larger compound from two smaller ones.
These types of reactions will often produce a solid
precipitate.
A compound that has formed after a chemical
reaction has taken place.
A Hoffman apparatus could be used to perform
this type of reaction with water as a reactant.
This is an organic compound that only contains
carbon and oxygen.
A compound or element that exists before a
chemical reaction occurs.
He created the first metal activity series.
We often use the metal activity series to
determine if this type of reaction will proceed.
This common oxide forms after hydrogen has
been involved in a combustion reaction.
He was able to develop the law of conservation of
mass through very precise experimentation.
This is an organic compound that only contains
hydrogen and carbon
Section III – Working with Chemical Equations (25 Marks)
1. Create balanced chemical equations for each of the following:
a. Doctors can sometimes treat acid indigestion by prescribing solid magnesium
hydroxide (milk of magnesia). The milk of magnesia reacts with the excess
stomach acid (hydrochloric acid – aqueous) to form water and an aqueous ionic
compound. (3 Marks [C])
b. Acids cannot be poured down the drain because they can react with certain salts
to form potentially deadly gases. For example, hydrogen sulfide gas (a poisonous,
rotten-egg smelling gas) is formed along with aqueous sodium chloride when
aqueous hydrochloric acid is poured down the drain and makes contact with solid
sodium sulfide. (3 Marks [C])
2. Predict the products formed by reactions in aqueous solutions of each of the following
pairs of compounds. In each case, write a balanced chemical equation indicating the
physical state of the products formed. (6 Marks [T/I])
a. Copper II Nitrate and Magnesium Chloride.
b. Ammonium Sulfide and Iron II Sulfate.
3. For each of the following, use the activity series to determine which reactions will proceed.
For the reactions that do occur, predict the products and complete and balance the
equation. For the reactions that will not occur, write “no reaction.” (6 Marks [T/I])
€
⎯→
a. Br2(l ) + KI(aq ) ⎯
b.
€
K 2 SO4 (aq ) + Al(s) ⎯
⎯→
c. Aqueous gold III chloride and metallic Sodium
d. Zinc metal and aqueous magnesium nitrate
4. Determine which of the following reactions will produce a precipitate. For those that do,
write both a balanced chemical equation and a net ionic equation. If no precipitate is
produced, write “no precipitate.” (7 Marks [T/I])
⎯→
a. KOH(aq ) + FeCl3(aq ) ⎯
€
b.
AgNO3(aq ) + CuBr2(aq ) ⎯
⎯→
€
⎯→
c. (NH 4 ) 2 S(aq ) + NaOH(aq ) ⎯
€
Section IV – Short Answer (15 Marks)
1. Carbon dioxide is a very common oxide that is formed as a result of a combustion reaction.
Briefly explain how this oxide is able to affect the pH of rainwater. (2 Marks [A])
2. Answer the following questions about combustion:
a. Using a simple word equation or skeleton equation, explain the difference between
complete and incomplete combustion (2 Marks [C])
b. One of the products of the incomplete combustion of a hydrocarbon is CO. Why is
CO harmful to humans? (2 Marks [A])
3. Read the following article about thermite and then answer the accompanying questions.
The Thermite Reaction
The thermite reaction (a type of aluminothermic reaction) is one in which aluminium metal is oxidized by an oxide of
another metal, most commonly iron oxide. (The name thermite is also used to refer to a mixture of two such
chemicals.) The products are aluminium oxide, free elemental metal, and a great deal of heat. The reactants are
commonly powdered and mixed with a binder to keep the material solid and prevent separation.
Iron oxide is the most commonly used oxide because it is very inexpensive, and molten iron is useful for welding.
However, other oxides are occasionally used for special purposes. In principle, another reactive metal could also
replace the aluminium. However this is almost never done because the properties of aluminium are ideal for this
reaction. For one thing, it is by far the cheapest of the highly reactive metals. Also, many other possible candidates do
not form a passivation layer as aluminium does, and consequently are much more dangerous to handle. However for
the purposes of this reaction the most important properties of aluminium are its relatively low melting point (660°C,
1221°F) and very high boiling point (2519°C, 4566°F). A low melting point means that it is relatively easy to melt the
metal, so that the reaction can occur mainly in the liquid phase (or rather, where the solid oxide particles meet the
liquid metal), and thus proceeds fairly quickly. On the other hand, a high boiling point enables the reaction to reach
very high temperatures, since several processes (e.g. loss of the fuel, and the heat it carries, as it boils away) would
tend to limit the maximum temperature to just below the boiling point. This 1900 K range for the liquid phase is quite
broad for any common metals (e.g. iron and copper are respectively 1320 and 1477 K), but is especially unusual
among the highly reactive metals (c.f. magnesium and sodium, respectively 440 and 785 K.)
Although the reactants are stable at room temperature, when they are exposed to sufficient heat to ignite (usually by
igniting with a burning magnesium ribbon; however, other methods are used as well, such as potassium permanganate
and glycerine, or a sparkler), they burn with an extremely intense exothermic reaction. The products emerge as liquids
due to the high temperatures reached (with iron (III) oxide, up to 2500°C (4500°F)— although the actual temperature
reached depends on how quickly heat can escape to the surrounding environment).
Thermite contains its own supply of oxygen, and does not require any external source (such as air). Consequently, it
cannot be smothered and may ignite in any environment (it will burn just as well while underwater, for example), given
sufficient initial heat. It cannot even be extinguished with water, as water sprayed on a thermite reaction will instantly
be boiled into steam. This, combined with the extremely high temperatures generated, makes thermite reactions
extremely hazardous even when appropriate precautions are taken.
Thermite reactions have many uses. It was originally used for repair welding in-place such things as locomotive axleframes where the repair can take place without removing the part from its installed location. Nations could use thermite
grenades in war to destroy sensitive equipment or documents when at imminent risk of capture. Thermite grenades
and bombs have been used in combat as incendiary devices, able to burn through heavy armor or other fireproof
barriers. Thermite can also be used for quickly cutting or welding metal such as rail tracks, without requiring complex or
heavy equipment. The mixture has been sold for many years under the trademark name Thermit for use in railroad
welding.
This type of reaction when used to purify the ores of some metals is called the Thermite process. An adaptation of the
thermite reaction, used to obtain pure uranium, was developed as part of the Manhattan Project at Ames Laboratory
under the direction of Frank Spedding. It is sometimes called the Ames process.
The thermite reaction can take place by accident in industrial locations where abrasive grinding and cutting wheels are
used with ferrous metals. Using aluminium in this situation produces a mixture of oxides that is capable of becoming a
violent explosive reaction.
a. Write the complete balanced equation for the thermite reaction. Remember that
the reactants are elemental aluminum and iron (III) oxide. Also, what type of
reaction is this? (3 Marks – T/I)
b. Why is the thermite reaction able to proceed underwater? Is this also why the
thermite reaction is dangerous? Explain. (3 Marks – T/I)
c. What are some of the civilian and military uses for the thermite reaction? (3 Marks
– A)