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1.      Chemists use equations to describe the changes that substances undergo.
2.      The physical state of substances in equations is shown by (g) for gas, (1) for liquid, (s) for
        solid, and (aq) for a water solution of the substance.
3.      Reactants are the starting substances in a reaction. Products are the substances resulting from
        a reaction.
4.      A chemical equation represents changes that take place in a reaction. It also shows relative
        amounts of reactants and products.
5.      Balancing an equation means adjusting coefficients so that there is the same number of atoms
        of each element on the left and right sides of the equation.
6.      Five general types of reactions are single displacement, double displacement, synthesis,
        decomposition, and combustion reactions.


1.   Write balanced equations for the following reactions.
a.   W03 +            H2     W            +       H20
b.   PdCI2 +          HN03        Pd(NO3)2        +    HCI
c.   RbBr +           AgCl        AgBr +          RbCl
d.   HfCl3 + Al  HfCl2 +          AlCI3
e.   Zn       +       CrCI3      CrCI2 +          ZnCI2
f.   BaCO3            +     C     +         H20        CO +       Ba(OH)2
g.   Cu + H2SO4            CuS04           +      S02 +      H20
h.   Pb(CH3COO)2(aq)        +     K2CrO4(aq)            PbCrO4(s)+KCH3COO(aq)
i.   RbCl(s)          +     02(g)          RbClO4(s)
j.   SiF4(s) + H20(l)      H2SiF6(aq) + H2SiO3(s)
k.   Sn(s) +          KOH(aq)  K2SnO2(s)          +    H2(g)
3. Substitute symbols and formulas for names and write balanced equations for each of the
   following reactions.

      a.     Chromium displaces hydrogen from hydrochloric acid, with chromium(II) chloride as
             the other product.
      b.     Barium hydroxide reacts with carbon dioxide to form barium carbonate and water.
      c.     Calcium carbonate decomposes to calcium oxide and carbon dioxide gas.
      d.     Calcium carbide, CaC2, reacts with water to produce calcium hydroxide and ethyne
             gas (acetylene), C2H2.
      e.     Hydrogen combines with sulfur to form hydrogen sulfide.

4.    Classify the following reactions as single displacement, double displacement,
      decomposition, synthesis, or combustion.

      a.     4Na(s) +        02(g)        2Na2O(s)
      b.     Pb(NO3)2(aq) + Na2CrO4(aq)            2NaNO3(aq)    +      PbCrO4(s)
      c.     Nbl3(s) +       I2(s)         NbI5(s)
      d.     2Li(s) + 2H20(l)     2LiOH(aq)        +     H2(g)
      e.     2C7Hl4(l)       +     2102(g)         14CO2(g)      +      14H20(g)

5.    Predict the products in the following reactions. Then write balanced equations.

      a.     decomposition of copper(II) oxide
      b.     copper and silver nitrate (displacement; copper(II) compound formed)
      c.     magnesium and oxygen (synthesis)
      d.     hydrochloric acid and silver nitrate (double displacement)
      e.     magnesium plus hydrochloric acid (displacement)
      f.     iron and oxygen (synthesis; iron(III) compound is formed)
      g.     iron and sulfur (synthesis; iron(II) compound is formed)
      h.     calcium hydroxide and sulfuric acid (double displacement)
      i.     zinc and sulfuric acid (single displacement)
      j.     benzene (C6H6) and oxygen (combustion reaction)
      k.     octane (C8H18) and oxygen (combustion reaction)

7.    Applying Dalton's atomic theory, explain why chemical equations must be balanced.

8.    Why is it that subscripts should not be changed in order to write a balanced chemical
9.    Nitric acid, HN03, ranks thirteenth on the list of chemicals produced in greatest amount in the
      United States. It has extensive use in industry. Nitric acid can be produced by the action of
      water on nitrogen trioxide. The balanced equation for the reaction is

                           3NO2(g) + H20(l)  2HN03(aq) + NO(g)

      Write a sentence that summarizes the information given in this equation.

10.   Iron occurs in the United States in the form of oxide ores such as iron(III) oxide, Fe2 O3 - In a
      blast furnace the iron ore is reduced to iron metal by carbon monoxide, which becomes
      carbon dioxide. Write a balanced equation for the process.

11.   Calcium chloride is used to melt ice or to keep it from forming on roads. This important
      compound can be produced by reacting calcium carbonate with hydrochloric acid. Two
      by-products are water and carbon dioxide. Write a balanced equation for the formation of
      calcium chloride by this reaction.

12.   Cyclopropane, C3H6, was once used with oxygen as a general anesthetic. Write a balanced
      equation for the complete combustion of cyclopropane.

13.   Aluminum hydroxide, AI(OH)3, is a component in many antacids. It neutralizes the HCI in
      stomach acid in a double displacement reaction. Write a balanced equation for this reaction.

14.   Ammonium nitrate, NH4NO3, is an important fertilizer and is also used in the manufacture of
      explosives and fireworks. It is produced by treating nitric acid, HN03, with ammonia gas,
      NH3 .
      a. Write a balanced equation for the reaction.
      b. What type of reaction is this?

15.   Two components of smog are NO and N02. N02 is formed in car engines and emitted into the
      atmosphere. When N02 is exposed to sunlight it forms NO and O atoms. What type of
      reaction is this?

16.   In the years following the French Revolution, Joseph Gay-Lussac made several important
      discoveries about how gases combine. For example, he noted that three volumes of hydrogen
      react with one volume of nitrogen to form two volumes of ammonia. Keep in mind that in
      those times, scientists did not know about atoms or the formulas of compounds.
      a.      Write a balanced chemical equation for this reaction.
      b.      How does this equation relate to Gay Lussac's findings?
      c.      What can you infer about the contents of two equal volumes of reacting gases?
      d.      What word could be substituted for the word volume to describe this reaction on the
              simplest level?
      e.      What type of reaction did Gay-Lussac perform?

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