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Chemical reactions tutorial

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					CHEMICAL REACTIONS TUTORIAL

                  Let’s get started!!
Goals

In this tutorial, you will learn…

 How to recognize 3 of the 5 types of reactions
 Predict the products of reactions when only
  given the reactants
What are the 5 types of
reactions?
                  Synthesis



       Double
                              Decomposition
    replacement




            Single
                         Combustion
         replacement
Which 3 will be we learning
about??
            Synthesis


          Decomposition


           Combustion
SYNTHESIS
Synthesis

 Two or more reactants combine to form…




 A + B  AB
 Synthesis Continued


2 Mg         +       O2  2 MgO
           Two reactants form one product

BUT WAIT!!
 Don’t forget about everything you have already
   learned! Is your equation balanced??
Predicting products
Before we keep going… lets learn a few things about
predicting products
Predicting products

 Here are a few important things to remember
  when predicting products:
   The compounds form must be neutral ionic
    compounds (which means you’ll be paying
    attention to their charges)
   You do NOT carry subscripts from the reactants to
    the products.
   You always balance your equation LAST
 Let’s go back to that
 synthesis example
  Remember the reaction:


 Mg          +      O2 
Helpful hint for later…why is
  oxygen O2 and not just O?
                                Click to find
                                  out why
Why O2??
  Oxygen is a diatomic molecule, which
  means when oxygen is by itself it must
  be O2. Remember that this DOES NOT
  mean that oxygen is O2 in compounds,
              only by itself!
 What are the other diatomic elements? (hint:
  remember the heavenly 7!



                                         Go back
Now to predict the products…

Mg    +     O2 
  Remember A + B  AB so Mg + O2
     will make a compound with
 magnesium and oxygen. What does a
   compound with magnesium and
          oxygen look like??
A compound with magnesium
and oxygen…

Magnesium is a metal, oxygen is a nonmetal so
 we must be forming an IONIC compound.


  What’s the charge of Mg?   What’s the charge of O?



                      2+           O 2-
     Mg
 So what’s the compound?



        Mg2+       O2-
Pick…

   MgO2              MgO

           Mg2O2
Nope!

                MgO2

           +2    +     2(-2)

        DOES NOT EQUAL ZERO


                               Try again!
Nope!

                  Mg2O2

          2(+2)    +   2(-2)   =0

 But remember ionic compounds need
       to be in the simplest form

                                    Try again!
Yes!     Very good!

 MgO is a neutral, correct ionic compound so
  our formula is

  Mg + O2  MgO
 Finally, balance the equation to satisfy the law
              of conservation of mass…

2Mg + O2  2MgO
So remember…

 When predicting products:
   Make correct ionic compounds
   THEN balance



Let’s move on to the rest of the reaction types…
Decomposition
Decomposition


 forms two or more products




 AB  A + B
Decomposition Continued

The electrolysis of water is when water
  decomposes into hydrogen and oxygen gas
  as shown below:


  2H2O  2H2 + O2
Predicting products and
decomposition
 Lets use that same reaction. What if we were
  not already given the products, how would
  we predict them?

 H2O  ??
                   Water is made of hydrogen and
                   oxygen, so will my products just
                            be H and O?
No!

 Remember, H and O are both diatomic
 elements.


H2O  H2 + O2
       But wait….something is
           still missing….
Balance!

 Don’t forget to balance your equation after
  you make your products! Your final answer
  should look like this:


  2H2O  2H2 + O2
You try one…

 What is the correct reaction for the
  decomposition of sodium chloride, NaCl?



      NaCl  Na + Cl                       2NaCl  Na2 + Cl2




                       2NaCl  2Na + Cl2
Nope!
                 NaCl  Na + Cl




 Don’t forget that chlorine is a diatomic
  element, so it must be Cl2




                                         Try again!
Nope!

                 2NaCl  Na2 + Cl2




 Although this reaction is correctly balanced,
  sodium is NOT a diatomic element




                                         Try again!
Yes!      Very good!

                  2NaCl  2Na + Cl2




 This is a correct reaction for the
  decomposition of sodium chloride.



Ready for the last type of reaction?
Combustion
Combustion
 Combustion is the burning of hydrocarbons.
                 Hydrocarbon?? What’s that?? Click
                           to find out!

  When a hydrocarbon reacts with oxygen (O2),
   the products are ALWAYS…..

Yes,   ALWAYS…
                  Carbon dioxide and water
                       CO2         + H 2O
Hydrocarbons

 A hydrocarbon is an organic molecule made
  up of hydrogen and carbon. Remember when
  we learned about these when we talked
  about organic chemistry??

     CH4                       C20H42


                  C6H10
Combustion Cont…

 Since the products of a combustion reaction
  are always CO2 and H2O, the hardest part
  about combustion reactions is balancing
  them

CH4 + O2  CO2 + H2O

                  Balance this equation…
Combustion Cont.

CH4 + O2  CO2 + 2H2O
 Be aware… this reaction was pretty easy to
  balance, some of the combustion reactions
  get pretty complicated! Like this one…

   4C3H9 + 21O2  12CO2 + 18H2O
Ready for your quiz??



                  Yes!




       Not quite, review the types of
           reactions with me…
Review
 Synthesis reactions: two or more reactants
 combine to form ONE product
                A + B  AB
 Decomposition reactions: ONE reactant
  breaks down into two or more products
                 AB  A + B
  Combustion reactions: a hydrocarbon reacts
   with oxygen to produce carbon dioxide and
   water.
          Hydrocarbon + O2  CO2 + H2O

                     Ok, now I’m ready for the quiz!
Quiz Question 1/5

 Which of the following is a decomposition
  reaction?


   2Fe + O2  2FeO                    Na + AgCl  Ag + NaCl




                     Na2S  2Na + S
Nope!

                 2Fe + O2  2FeO




 This is two reactants forming ONE product
  which is an example of a synthesis reaction




                                           Try
                                          again!
Nope!
                 Na + AgCl  Ag + NaCl




 This reaction does not just form one product.
  This reaction is an example of a single
  replacement reaction which we will learn
  about later.


                                           Try
                                          again!
Yes!     Very good!

                  Na2S  2Na + S




 This reaction is ONE reactant breaking down
  into two or more products, which is an
  example of a decomposition reaction.
                                       Back to the
                                        question!

                                             Next
                                           question!
Quiz Question 2/5

  How can you recognize a combustion
     reaction?


A combustion reaction
                         A combustion reaction   A combustion reaction
  is the only reaction
                              always has a            always has a
  always has at least
                         hydrocarbon reacting    hydrocarbon reacting
two reactants and two
                             with oxygen to      with nitrogen, which is
 products. One of the
                            produce carbon          a very explosive
  reactants is always
                           dioxide and water.           reaction.
      oxygen gas.
Nope!
                A combustion reaction
                  is the only reaction
                  always has at least
                two reactants and two
                 products. One of the
                  reactants is always
                      oxygen gas.


 We will learn about other reactions that can
  have more than one product and more than
  one reactant. This is NOT the way to identify
  a combustion reaction.

                                          Try again!
Nope!
                 A combustion reaction
                      always has a
                 hydrocarbon reacting
                 with nitrogen, which is
                    a very explosive
                        reaction.




 Although combustion reactions are typically
  explosive, it is not because they react with
  nitrogen.


                                           Try again!
Yes!     Very good!

                A combustion reaction
                     always has a
                hydrocarbon reacting
                    with oxygen to
                   produce carbon
                  dioxide and water.




 This is how we identify a combustion reaction


                                         Back to
                                                      Next
                                           the
                                                    question!
                                        question!
Quiz Question 3/5

 Pick correct bubble that finishes the reaction
    below.

                  K + Cl2  ??
2K + Cl2  2KCl                       K + Cl2  KCl



                    K + Cl2  KCl2
Nope!
                   K + Cl2  KCl2




 Remember to not carry subscripts over to
  your products. K has a +1 charge and Cl has a
  -1 charge so the product of KCl2 is not neutral
  and cannot be correct.
                                               Try
                                              again!
Almost!        But not quite…

                     K + Cl2  KCl




 Although this product is correct, the equation
  is not balanced!



                                              Try
                                             again!
Yes!     Very good!

                  2K + Cl2  2KCl




 The products are correct and the reaction is
  balanced! Great job!


                                     Back to
                                                  Next
                                       the
                                                question!
                                    question!
Quiz Question 4/5

 Pick correct rectangle that finishes the
  reaction below.

                    C2H8 + O2  ??

  C2H8 + O2 CO2 + H2O                 C2H8 + 4O2 2CO2 + 4H2O




                   C2H8 + O2 C2H8O2
Almost, but not quite…

               C2H8 + O2 CO2 + H2O



 Great job predicting the products, but….
  don’t forget to balance!!




                                        Try again!
Nope!
                C2H8 + O2 C2H8O2




 Remember that combustion reactions always
 have carbon dioxide and water as products




                                     Try again!
Yes!     Very good!

                C2H8 + 4O2 2CO2 + 4H2O




 Products are correct and the equation is
  correctly balanced. Great job!


                                          Back to the
                                           question!

                                            Next
                                          question!
Quiz Question 5/5

 Pick correct rectangle that finishes the
  reaction below.

              Al + N2  ??
   Al + N2  AlN2



                    3Al + N2  Al3N2



                                       2Al + N2  2AlN
Nope!

                   Al + N2  AlN2




 Remember we do not carry over subscripts.
  Aluminum has a +3 charge and nitrogen has a
  -3 charge so a formula of AlN2 is not a neutral
  compound


                                          Try again!
Nope!

                 3Al + N2  Al3N2




 Although this equation is balanced, since
  aluminum has a +3 charge and nitrogen has a
  -3 charge, this is not a neutral compound



                                       Try again!
Yes!     Very good!

                 2Al + N2  2AlN




 A correct neutral compound for the product
  and a balanced equation. Great!


                                       Back to the
                                        question!

                                         Finish!
Congratulations!
You have finished the chemical reactions tutorial




                                                    Go back
                                                     to the
                                                      start

				
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posted:11/23/2012
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