Lets get started How do you know when a chemical reaction takes place Color Change Precipitate Formation How do you know when a chemical reaction takes place Gas Formation Odor How do you know when a chemical reaction takes place ID: 800010
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Slide1
Chemical reactions tutorial
Let’s get started!!
Slide2How do you know when a chemical reaction takes place?
Color Change
Precipitate Formation
Slide3How do you know when a chemical reaction takes place
?
Gas Formation
Odor
Slide4How do you know when a chemical reaction takes place?
Temperature Change
Change in Acidity
Slide5Symbols used in Chemical Equations
Symbol
Purpose
(s)
Identifies a solid state
(l)
Identifies liquid state
(g)
Identifies gaseous state
(
aq
)
Identifies that something is dissolved in water
Slide6Goals
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
Slide7What are the 5 types of reactions?
Slide8Which 3 will be we learning about??
Slide9Synthesis
Two or more reactants combine to form…
ONE PRODUCT!!
A + B
AB
Slide10Synthesis Continued
Mg + O
2
MgOTwo reactants form one product
BUT WAIT!!
Don’t forget about everything
you have already learned!
Is your equation balanced??
2
2
Slide11Before we keep going… lets learn a few things about predicting products
Predicting products
Slide12Predicting 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
Slide13Ionic Charges
Slide14Let’s go back to that synthesis example
Remember the reaction:
Mg + O
2
Helpful hint for later…why is oxygen O
2
and not just O?
Click to find out why
Slide15Why O2
??
What are the other diatomic elements? (hint: remember the heavenly 7!
Oxygen is a diatomic molecule, which means when oxygen is by itself it must be O
2. Remember that this DOES NOT mean that oxygen is O
2 in compounds, only by itself!
Go back
H
2
I
2
Br
2
O
2
N
2
Cl
2
F2
Slide16Now to predict the products…
Remember A + B
AB so Mg + O
2
will make a compound with magnesium and oxygen. What does a compound with magnesium and oxygen look like??
Mg + O
2
Slide17A 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?
Mg 2+
What’s the charge of O?
O
2-
Slide18So what’s the compound?
Mg
2+
O
2-
Pick…
MgO
2
Mg
2
O
2
MgO
Slide19Nope!
+2 + 2(-2)
DOES NOT EQUAL ZERO
MgO
2
Try again!
Slide20Nope!
2(+2) + 2(-2) = 0
But remember ionic compounds need to be in the simplest form
Mg
2
O
2
Try again!
Slide21Yes! Very good!
MgO
is a neutral, correct ionic compound so our formula is
Mg + O
2
MgO
Finally, balance the equation to satisfy the law of conservation of mass…
2Mg + O
2
2MgO
Slide22So remember…
When predicting products:
Make correct ionic compounds
THEN balance
Let’s move on to the rest of the reaction types…
Slide23Essentially the OPPOSITE of a synthesis reaction
Decomposition
Slide24Decomposition
forms two or more products
ONE REACTANT…
A + B
AB
Slide25Decomposition Continued
The electrolysis of water is when water decomposes into hydrogen and oxygen gas as shown below:
2H
2
O 2H2 + O
2
Slide26Predicting products and decomposition
Lets use that same reaction. What if we were not already given the products, how would we predict them?
H
2
O ??
Water is made of hydrogen and oxygen, so will my products just be H and O?
Slide27No!
Remember, H and O are both diatomic elements.
H
2
O H2 + O
2
But wait….something is still missing….
Slide28Balance!
Don’t forget to balance your equation after you make your products! Your final answer should look like this:
2H
2
O 2H2
+ O2
Slide29You try one…
What is the correct reaction for the decomposition of sodium chloride,
NaCl
?
NaCl
Na + Cl
2NaCl 2Na + Cl
2
2NaCl
Na
2
+ Cl
2
Slide30Nope!
Don’t forget that chlorine is a diatomic element, so it must be Cl
2
NaCl
Na + Cl
Try again!
Slide31Nope!
Although this reaction is correctly balanced, sodium is NOT a diatomic element
2NaCl
Na
2
+ Cl2
Try again!
Slide32Yes! Very good!
This is a correct reaction for the decomposition of sodium chloride.
2NaCl
2Na + Cl
2
Ready for the last type of reaction?
Slide33Combustion
Slide34Combustion
Combustion is the burning of hydrocarbons.
Hydrocarbon?? What’s that?? Click to find out!
When a hydrocarbon
reacts with oxygen (O
2
), the products are ALWAYS…..
Yes,
ALWAYS…
Carbon
dioxide and water
CO
2
+ H
2
O
Slide35Hydrocarbons
A hydrocarbon is an organic molecule made up of hydrogen and carbon. Remember when we learned about these when we talked about organic chemistry??
CH
4
C
6
H10
C
20
H
42
Slide36Combustion Cont…
Since the products of a combustion reaction are always CO
2
and H2
O, the hardest part about combustion reactions is balancing them
CH4
+ O2
CO
2
+ H
2
O
Balance this equation…
Slide37Combustion Cont.
Be aware… this reaction was pretty easy to balance, some of the combustion reactions get pretty complicated! Like this one…
CH
4
+
2O
2
CO
2
+
2
H
2
O
4
C
3
H9 + 21O2 12CO2 + 18H2O
Slide38Combustion Cont.
The trick to balancing combustion equations:
Balance the C and H first
Then balance the O lastREMEMBER, account for both
oxygens on CO2 and H2O
Slide39Ready for your quiz??
Yes!
Not quite, review the types of reactions with me…
Slide40Review
Synthesis reactions
: two or more reactants combine to form ONE product
A + B
AB
Decomposition reactions
: ONE reactant breaks down in
to two or more
products
AB
A + B
Combustion reactions
: a hydrocarbon
reacts with oxygen to produce carbon dioxide and water.
Hydrocarbon + O
2
CO2 + H2OOk, now I’m ready for the quiz!
Slide41Quiz Question 1/5
Which of the following is a decomposition reaction?
2Fe + O
2
2FeO
Na + AgCl Ag +
NaCl
Na
2
S
2Na + S
Slide42Nope!
This is two reactants forming ONE product which is an example of a
synthesis
reaction
2Fe + O2
2FeO
Try again!
Slide43Nope!
This reaction does not just form one product. This reaction is an example of a single replacement reaction which we will learn about later.
Na +
AgCl
Ag + NaCl
Try again!
Slide44Yes! Very good!
This reaction is ONE reactant breaking down into two or more products, which is an example of a decomposition reaction.
Na
2
S
2Na + S
Next question!
Back to the question!
Slide45Quiz Question 2/5
How can you recognize a combustion reaction?
A combustion reaction is the only reaction always has at least two reactants and two products. One of the reactants is always oxygen gas.
A combustion reaction always has a hydrocarbon reacting with oxygen to produce carbon dioxide and water.
A combustion reaction always has a hydrocarbon reacting with nitrogen, which is a very explosive reaction.
Slide46Nope!
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!
A combustion reaction is the only reaction always has at least two reactants and two products. One of the reactants is always oxygen gas.
Slide47Nope!
Although combustion reactions are typically explosive, it is not because they react with nitrogen.
Try again!
A combustion reaction always has a hydrocarbon reacting with nitrogen, which is a very explosive reaction.
Slide48Yes! Very good!
This is how we identify a combustion reaction
Next question!
A combustion reaction always has a hydrocarbon reacting with oxygen to produce carbon dioxide and water.
Back to the question!
Slide49Quiz Question 3/5
Pick correct bubble that finishes the reaction below.
K + Cl
2
??
2K + Cl2 2KCl
K + Cl
2
KCl
2
K + Cl
2
KCl
Slide50Nope!
Remember to not carry subscripts over to your products. K has a +1 charge and
Cl
has a -1 charge so the product of KCl
2 is not neutral and cannot be correct.
Try again!
K + Cl2 KCl
2
Slide51Almost! But not quite…
Although this product is correct, the equation is not balanced!
Try again!
K + Cl
2
KCl
Slide52Yes! Very good!
The products are correct and the reaction is balanced! Great job!
Next question!
2K + Cl
2
2KCl
Back to the question!
Slide53Quiz Question 4/5
Pick correct rectangle that finishes the reaction below.
C
2
H8 + O2 ??
C2H8
+ O2 CO2 + H2O
C
2
H
8
+ O
2
C
2
H
8
O
2C2H8 + 4O2 2CO2 + 4H2O
Slide54Almost, but not quite…
Great job predicting the products, but…. don’t forget to balance!!
Try again!
C
2
H
8 + O2 CO2 + H
2
O
Slide55Nope!
Remember that combustion reactions always have carbon dioxide and water as products
Try again!
C
2
H
8 + O2 C2H
8
O
2
Slide56Yes! Very good!
Products are correct and the equation is correctly balanced. Great job!
Back to the question!
Next question!
C
2
H
8
+ 4O
2
2CO
2
+ 4H
2
O
Slide57Quiz Question 5/5
Pick correct rectangle that finishes the reaction below.
Al + N
2
??
Al + N2 AlN
2
3Al + N
2
Al
3
N
2
2Al + N
2
2AlN
Slide58Nope!
Remember we do not carry over subscripts. Aluminum has a +3 charge and nitrogen has a -3 charge so a formula of AlN
2
is not a neutral compound
Try again!
Al + N
2 AlN2
Slide59Nope!
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!
3Al + N
2
Al3N
2
Slide60Yes! Very good!
A correct neutral compound for the product and a balanced equation. Great!
Finish!
Back to the question!
2Al + N
2
2AlN
Slide61You have finished the chemical reactions tutorial
Congratulations!
Go back to the start