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Grade 12 chemistry questions Exercises: Writing Balanced Equations (Use after Lab E.

Grade 12 chemistry questions

Exercises: Writing Balanced Equations (Use after Lab E.4)
When writing the balanced equation for the following questions be sure to include states of matter of all reactants and products.

Note: Remember to read the balanced equations in terms of moles.

Iron pipes are strongly attacked and corroded by hydrosulfuric acid. This problem is very serious for “sour” natural gas wells—wells that contain sulfur compounds as well as methane. (Iron(II) sulfide is one product.)
Reaction type:

Balanced equation:

Word equation:

Iron rusts in moist air to cause millions of dollars damage each year.
Reaction type:

Balanced equation:

Word equation: iron + water + oxygen iron(III) oxide trihydrate (or iron(III) hydroxide)

Coal (assume a simple formula of C9H6) undergoes complete combustion.
Reaction type:

Balanced equation:

Word equation:

The first recorded observation of hydrogen gas was made by Paracelsus (1493-1541) when he added iron to sulfuric acid. (An iron(II) compound is one substance formed.)
Reaction type:

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In 1783 hydrogen and oxygen were first reacted by Henry Cavendish to produce water, and in 1937 the Hindenberg, a hydrogen-filled dirigible, exploded by the same reaction.
Reaction type:

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Magnesium will continue to burn when lowered into a flask of carbon dioxide.
Reaction type:

Balanced equation:

Word equation: magnesium + carbon dioxide In the iron exchange method of water softening, sodium zeolite (Na2Ze, where Ze represents a very complex ion) removes calcium ions from hard water by precipitation. (Sodium zeolite, unlike most sodium compounds, is not soluble in water.)
Reaction type:

Balanced equation: ____ Na2Ze( ) + ____ CaSO4(aq)

Word equation:

The sodium zeolite may be regenerated by reversing a brine (NaCl) solution through the water softener.
Reaction type:

Balanced equation:

Word equation: calcium zeolite + sodium chloride

Temporary hard water may be softened by heating.
Reaction type:

Balanced equation: ____ NaHCO3(aq) ____ Na2CO3(aq) + ____ CO2(g) + ____ H2O(l)

Word equation:

Soap may react with hard water to precipitate bathtub-ring.
Reaction type:

Balanced equation: ____ NaC17H35COO(aq) + ­­­­­_______________

Word equation: _______________ + magnesium sulfate(aq)

Bottles of Sani-Flush carry a warning that dangerous fumes are produced by using Sani-Flush (NaHSO4) together with chlorine bleach.
Reaction type:

Balanced equation: ___NaHSO4(aq) + ___NaClO(aq) + ___NaCl(aq) ___Cl2(g) + ___H2O(l) + ___Na2SO4(aq)

Word equation:

Joseph Priestley (1733-1804) in one of his many experiments with mercury decomposed cinnabar (mercury(II) sulfide).
Reaction type:

Balanced equation:

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In 1784 Nicolas Leblanc discovered a new, economical preparation for soda ash (Na2CO3) and caustic soda (NaOH). (Questions 13 to 15.)

First, Leblanc reacted rock salt (NaCl(s)) with oil of vitriol (H2SO4(aq)).
Reaction type:

Balanced equation:

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Second, he reacted the sodium sulfate(s) from Equation 13 with charcoal and limestone.
Reaction type:

Balanced equation: ___________ + ___________ + ___________ ___Na2CO3(s) + ___CaS(s) + ___CO2(g)

Word equation: ____________ + carbon + calcium carbonate

And last, Leblanc dissolved some of the soda ash from Equation 14 and reacted it with slaked lime (Ca(OH)2(s)).
Reaction type:

Balanced equation:

Word equation:

In 1807 Humphry Davy jumped around in wild excitement when he discovered potassium by electrically decomposing molten potash (potassium chloride).
Reaction type:

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Bread dough is caused to rise by producing carbon dioxide from cream of tartar (potassium hydrogen tartrate) and baking soda.
Reaction type:

Balanced equation: ___KHC4H4O6(aq) + _________ ___KNaC4H4O6(aq) + ___H2O(l) + ___ CO2(g)

Word equation: ____________ + sodium hydrogen carbonate

A boric acid solution is used in laboratory eyewashes to neutralize an ammonium hydroxide solution splashed into a student’s or technician’s eye.
Reaction type:

Balanced equation:

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Overview of Chemical Reactions (Use after Lab E.11)
List four pieces of evidence for the occurrence of a chemical reaction.


List the six reaction types identified in this unit.


Compare the physical state of ionic vs. molecular substances.


Write (aq) beside the soluble substances and (s) beside the low solubility substances below.

KNO3 ( )

Ca3(PO4)2 ( )

H2SO3 ( )

Pb(CH3COO)2 ( )

(NH4)2SO4 ( )

Ba(OH)2 ( )

PbI2 ( )

Ag2S ( )

Cu ( )

Write the proper phase (s), (l), (g), or (aq) next to the substances in the following balanced equations.

2 Na( ) + 2 HOH( ) H2( ) + 2 NaOH( )

2 HgO( ) 2 Hg( ) + O2( )

Ba(OH)2(aq) + H2SO3(aq) 2 HOH( ) + BaSO3( )

When writing balanced chemical equations for the following reactions provide the state of matter
for all reactants and products.

A freshly scraped piece of aluminum reacts with oxygen from the air to form a protective coating.
Reaction type:

Balanced equation:

Word equation:





Without the oxide coating formed in Equation 19, aluminum would react with hot water.
Reaction type:

Balanced equation:

Word equation:

Pure zinc is a reactive metal and yet it is used to galvanize other metals. Zinc reacts with both oxygen and carbon dioxide in the air to produce a zinc oxide and zinc carbonate protective coating.
Reaction type:

Balanced equation:

Word equation:

Milk of magnesia (Mg(OH)2(s)) is taken as an antacid to neutralize excess stomach acid, (HCl(aq)).
Reaction type:

Balanced equation:

Word equation:

Dry chemical fire extinguishers depend upon the heat of the fire to decompose the sodium hydrogen carbonate into sodium carbonate, carbon dioxide and water vapor. (The cheapest dry chemical fire extinguisher for small fires is baking soda.)
Reaction type:

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An oxy-acetylene torch burns acetylene (C2H2(g)) to produce enough heat to melt steel.
Reaction type:

Balanced equation:

Word equation:
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Grade 12 chemistry questions
Exercises: Writing Balanced Equations (Use after Lab E.4)
When writing the balanced equation for the following questions be sure to include states of
matter of all...

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