Tuesday 3/26/13: PREDICTING PRODUCTS
REVIEW INFORMATION:
A. Equations show:
1.) The reactants that enter a reaction
2.) The products that are formed by the reaction (rxn)
Example:
CO2 + H2O  H2CO3
Reactants
Product
B. Predicting Products
1.) The products of a chemical reaction may often be predicted by applying known facts about
common reaction types.
2.) There are hundreds of different ”kinds” of chemical reactions, only four general types
of reactions will be considered: single displacement, double displacement, decomposition,
and synthesis.
Single Displacement
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General form of a single displacement: element + compound  element + compound
A + BC  AC + B or A + BC  BA + C
Example 1: Fe(c) + Cu(NO3)2(aq)  Fe(NO3)2(aq) + Cu(c)
Example 2: 2Na(c) + 2H2O(l)  2NaOH(aq) + H2(g)
Double Displacement
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The positive and negative ions of two compounds are interchanged
compound + compound  compound + compound
A+X- + B+Y-  A+Y- + B+XExample: 2KOH(aq) + H2SO4(aq)  K2SO4 (aq) + H2O(l)
Decomposition
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When energy in the form of heat, electricity, light, or mechanical shock is supplied, a
compound may decompose to form simpler compounds and/or elements.
The general form for this type of reaction: compound  two or more substances
AB  A + B
Example: 2KClO3(c)  2KCl(c) + 3O2(g)
Synthesis
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In a synthesis reaction two or more simple substances (compounds and/or elements) are
combined to form one new and more complex substance.
The general form is : Element + element  compound or
compound + compound  compound
A + X  AX
Example 1: 2Na(c) + Cl2(g)  2NaCl(c)
Example 2: SO2(g) + H2O(1)  H2SO3(aq)
PRACTICE PREDICTING PRODUCTS: For each of the following word equations identify the
type or rxn, predict the products(s), write the complete skeleton equation, and balance the
equation.
1.) silver nitrate + zinc chloride  ________________________________________________
Type of rxn: ____________________________________
Skeleton equation: AgNO3
+
ZnCl2  __________________________________________
Balanced equation: ______________________________________________________________
---------------------------------------------------------------------------------------------------------------------------2.) zinc + hydrochloric acid  _____________________________________________________
Type of rxn: _____________________________________
Skeleton equation: Zn + HCl  ___________________________________________________
Balanced equation:
_______________________________________________________________
---------------------------------------------------------------------------------------------------------------------------3.) aluminum + oxygen  _________________________________________________________
Type of rxn: ______________________________________
Skeleton equation:
Al + O2  ___________________________________________________
Balanced equation: ______________________________________________________________
---------------------------------------------------------------------------------------------------------------------------4.) HgO  _____________________________________________________________________
Type of rxn: _______________________________________
Skeleton equation: _______________________________________________________________
Balanced equation: ______________________________________________________________
WAVES
Scientists have observed that many elements emit (give off) visible light when they are heated in a flame. The
light that each element emits is related to the arrangement of the electrons in its atoms. This light is a type of
electromagnetic radiation (energy) that acts like a wave. There are different types of waves, some visible to
us and others that we cannot see. Below is the electromagnetic spectrum, which arranges all these waves
according to their wavelengths and frequencies:
All waves have similar characteristics and components:
Visible light
Wavelength
Wavelength is the distance between two consecutive troughs or two consecutive crests. The symbol used for
wavelength is the Greek letter lambda (λ). It is usually measured in meters (m), centimeters (cm), or
nanometers (nm, 1 nm = 1 x 10-9 m). Frequency (represented by ν, the Greek letter nu) is the number of
wavelengths that pass a given point per second. The unit for frequency is the Hertz (Hz, waves per second).
Different waves have different wavelengths and frequencies. The following are the relationships between
wavelength and frequency:
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As the wavelength increases, the frequency decreases
As the wavelength decreases, the frequency increases
Light, emitted by atoms of elements, is a form of energy. This energy is related to the wavelength and
frequency of the light emitted through the following formulas:
c=λxν
- c is the speed of light (3.00 x 108 meters / second)
- λ is the wavelength of the wave
- ν is the frequency of the wave
Ephoton = h x ν
- Ephoton is energy
- h is Planck’s constant (6.626 x 10-34 J s)
- ν is the frequency of the wave
Using the previous information, solve the following problems:
1. What is the frequency of green light, which has a wavelength of 4.90 x 10-7 m?
2. An X-ray has a wavelength of 1.15 x 10-10 m. What is its frequency?
3. A popular radio station broadcasts with a frequency of 94.7 MHz. What is the
wavelength of the broadcast? (1 MHz = 106 Hz)
4. Tiny water drops in the air disperse the white light of the sun into a rainbow.
What is the energy of a photon from the violet portion of the rainbow if it has a
frequency of 7.23 x 1014 Hz?
5. What is the energy of each of the following types of radiation and what type of
radiation is it (use the electromagnetic spectrum to determine the type of
radiation)?
a. 6.32 x 1020 Hz
b. 9.50 x 1013 Hz
c. 1.05 x 1016 Hz