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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?. Which 3 will be we learning about??. SYNTHESIS.

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chemical reactions tutorial

Chemical reactions tutorial

Let’s get started!!

goals
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
synthesis1
Synthesis
  • Two or more reactants combine to form…

ONE PRODUCT!!

AB

A + B 

synthesis continued
Synthesis Continued

Mg + O2 MgO

Two reactants form one product

2

2

BUT WAIT!!

Don’t forget about everything you have already learned! Is your equation balanced??

predicting products
Predicting products

Before we keep going… lets learn a few things about predicting products

predicting products1
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
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 o 2
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!

F2

H2

Br2

N2

I2

Cl2

O2

Go back

now to predict the products
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
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?

O 2-

Mg 2+

so what s the compound
So what’s the compound?

Mg2+

O2-

Pick…

MgO2

MgO

Mg2O2

slide15
Nope!

MgO2

+2 + 2(-2)

DOES NOT EQUAL ZERO

Try again!

slide16
Nope!

Mg2O2

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

But remember ionic compounds need to be in the simplest form

Try again!

yes very good
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
So remember…
  • When predicting products:
    • Make correct ionic compounds
    • THEN balance

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

decomposition1
Decomposition

ONE REACTANT…

forms two or more products

A + B

AB 

decomposition continued
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
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?

slide23
No!
  • Remember, H and O are both diatomic elements.

H2O  H2 + O2

But wait….something is still missing….

balance
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
You try one…
  • What is the correct reaction for the decomposition of sodium chloride, NaCl?

NaCl Na + Cl

2NaCl  Na2 + Cl2

2NaCl  2Na + Cl2

slide26
Nope!

NaCl Na + Cl

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

Try again!

slide27
Nope!

2NaCl  Na2 + Cl2

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

Try again!

yes very good1
Yes! Very good!

2NaCl  2Na + Cl2

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

Ready for the last type of reaction?

combustion1
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 + H2O

hydrocarbons
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??

C20H42

CH4

C6H10

combustion cont
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 cont1
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
Ready for your quiz??

Yes!

Not quite, review the types of reactions with me…

review
Review
  • Synthesis reactions: two or more reactants combine to form ONE product

A + B  AB

  • Decomposition reactions: ONE reactant breaks down into two or moreproducts
  • 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
Quiz Question 1/5
  • Which of the following is a decomposition reaction?

2Fe + O2 2FeO

Na + AgCl Ag + NaCl

Na2S  2Na + S

slide37
Nope!

2Fe + O2 2FeO

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

Try again!

slide38
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 good2
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
Quiz 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.

slide41
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!

slide42
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 good3
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 the question!

Next question!

quiz question 3 5
Quiz Question 3/5
  • Pick correct bubble that finishes the reaction below.

K + Cl2 ??

K + Cl2 KCl

2K + Cl2 2KCl

K + Cl2 KCl2

slide45
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
Almost! But not quite…

K + Cl2 KCl

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

Try again!

yes very good4
Yes! Very good!

2K + Cl2 2KCl

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

Back to the question!

Next question!

quiz question 4 5
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 quite1
Almost, but not quite…

C2H8 + O2 CO2 + H2O

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

Try again!

slide50
Nope!

C2H8 + O2 C2H8O2

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

Try again!

yes very good5
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
Quiz Question 5/5
  • Pick correct rectangle that finishes the reaction below.

Al + N2 ??

Al + N2  AlN2

3Al + N2 Al3N2

2Al + N2 2AlN

slide53
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!

slide54
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 good6
Yes! Very good!

2Al + N2 2AlN

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

Back to the question!

Finish!

congratulations
Congratulations!

You have finished the chemical reactions tutorial

Go back to the start

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