Writing and Balancing Chemical Equations
Problem Set #3
Previously we practiced balancing chemical equations using 1) The Particle Pic Method (JE #8) and 2) The Inventory
Method (JE #9). This time your assignment is to write the balanced chemical equations from written sentences. You
already know why copper(II) sulfate is written as CuSO4. Do you also remember the 7-Up method for the diatomic
molecules? Oxygen gas, for example, is not written as O, but as O2 because two oxygen atoms form covalent bonds in
order to form a diatomic molecule. Conversely, metals such as sodium, iron and zinc can exist as elemental atoms and
can be written Na, Fe and Zn in a chemical equation providing they are not in a compound with one or more other elements.
Do all of these problems on a separate sheet of paper (and not in your journal)
Part I Directions
Balance the equations (a-h) in problem #42 on page 168 in the textbook. This will give you some additional
practice for Quiz 5.1. Show your work using the atomic inventory method. You may use the particle pics
method if you prefer, but remember, this method is more time consuming.
Part II Directions
1) Read the word equation carefully. You will need to determine which substances are the reactants and which
ones are the products. If you are having difficulty identifying then try underlining them first.
2) Write the unbalanced chemical equation from the word equation.
3) Balance the equation using the Atomic Inventory method.
Sample Problem #1
Bromine gas and nitrogen gas are ignited with a spark and produce gaseous nitrogen tribromide
Step one: read the equation carefully
Step two: Br2 + N2  NBr3
Solution: 3Br2 + N2  2NBr3
Sample Problem #2
Magnesium metal when mixed with silver nitrate solution produces magnesium nitrate and silver metal
Solution: Mg + 2 AgNO3  Mg(NO3)2 + 2 Ag
1. Iron metal reacts with oxygen gas in the bright sunlight to produce rust (iron (III) oxide).
Hint: Remember to use the “swap and drop” method for writing the formula for iron oxide.
2. Magnesium metal is burned in oxygen gas to produce solid magnesium oxide.
3. Aluminum metal and aqueous copper (II) chloride are placed in an electric current to produce copper metal and
aqueous aluminum chloride (AlCl3).
4. Oxygen gas and chlorine gas are heated in the presence of potassium solid to form potassium chlorate (KClO3).
5. Carbon monoxide gas reacts with sulfur trioxide producing a bright light, carbon dioxide gas and sulfur dioxide gas.
6. Ethane (C2H6) gas combines with oxygen gas to produce a bright flame, carbon dioxide gas and water vapor.
7. Iron oxide is heated in carbon monoxide gas to produce molten elemental iron and carbon dioxide gas.
8.
Iron (III) phosphate solution and nickel metal react to produce iron powder and nickel(II) phosphate (Ni3(PO4)2) solution.
The reaction must be heated to produce results.