Mole Calculations with Energy

Today we learned about mole calculations with energy.

This involves enthalpy, delta H. Delta H is expressed as a kJ/mole.

 To convert:
Moles to energy ----> 1kJ/mole

Energy to moles----> 1 mole/ 1 kJ


Here are some examples.

E.g.
CuO (s) + H2(g) + 135.0 kJ ----> Cu(s) + H2) (l)

Calculate energy absorbed for 6.0 moles of  CuO reacting.

130.5 kJ/mole x 6 moles = 780 kJ

Calculate the amount of energy released when 6.00 grams of Carbon are combined with O2 to form CO2 gas.

C(s) + O2(g) -----> CO2(g) + 393.5 kJ
First you convert grams to moles:

6.00g C (1 mole C/ 12.0107 g)

Then you multiply by (393.5 kJ/ 1mole C) and you get 196.57 kJ.

Piece of cake!


Unfortunately no videos were found. But...

Exothermic and Endothermic Reactions

Today we learned about endothermic and exothermic reactions.

Exothermic reactions are reactions that give off energy.
Endothermic reactions absorb energy. 

Today we also discovered the joy of energy diagrams. These show the energy of the reactants and the energy of the products.

 The reaction is exothermic because, the energy of products is less than energy of reactants. This means energy was released.

The x axis represents the time needed to undergo the reaction and the y-axis represents potential energy in kJ.

The diagram is very straightforward.

The initial flat line represents the energy of the reactants. As you can see, the line transforms into a hill. The distance between the initial flat line and the top of the hill is called the activation energy.This is the amount of energy needed to carry out the reaction.  The level of the hill (on the y axis) is called the activated complex. It is the highest amount of energy that the reactants can reach in the reaction process. The curve then drops off and then evens out. The distance between the energy of the reactants line and the energy of the products is known as delta H. Delta H is the change in enthalpy,(heat contained in the system).

This is found using the equation
Delta H = energy of products - energy of the reactants.
A negative value of H  signifies an exothermic reaction because you end up with less energy than you started with.

A positive value of H signifies and endothermic reaction because you end up with less energy than you started with.

Once H is found, you use it in chemical equations like this

Mg + Cl2 ------> MgCl2 + 347 kJ

Notice that the 347 is on the side of the reactants. This means that the reaction is exothermic because:

Energy on one side = energy on the other
So the MgCl2 needs the 347 kJ to make up the energy so it equals the reactants.
This means that the reaction released energy.

Quiz

We had a quiz today in Chemistry.

It was on balancing and predicting products of chemical equations
It covered everything we had been learning until now.
Types of reactions
Prediction Products
Net Ionic Equations
Solubility
Balancing equations


It was fun!

Advanced Double Replacement

Remember double replacement?
Now we have double replacement with solubility.

Now we have to put the states of matter signs beside in compound in a balanced equation
E.g. (g), (l), (aq), (s)

Lets take a double replacement reaction.

2 K3PO3 + 3Cu(NO3)2 -------> 1Cu3(PO3)2 + 6 KNO3

http://nobel.scas.bcit.ca/chem0010/unit8/solubilityRules.htm Here are the solubility rules:

Look at the products. Use the solubility sheet to see whether Cu will react with PO3. Do the same for K and NO3
Since Cu and PO3 do not react, they are a solid (s).
K and NO3 do react and will be (aq)
It will look like this:

2K3PO3 + 3 Cu(NO3)2 ------> 1 Cu3(PO3)2 (s) + 6 KNO3(aq)

The equation will look like this

2K3PO3 (aq) + Cu(NO3)2(aq) -----> 1 Cu3(PO3)2 (s)  + 6 KNO3(aq)

Lab 5 B

Today we did a great lab in class:

There were 7 reactions that we observed and each one was amazing!

Here they are:

Reaction 1: We held a piece of copper wire in the hottest part of a bunsen burner flame for several minutes and recorded our observations:

Reaction 2: We took a nail, and cleaned it, then we submerged half the nail in liquid copper (II) sulfate solution. 15 minutes later, the part of the nail that was submerged was coated with copper.

Reaction 3: We heated some copper (II) sulfate(s) as we have already done(we are experts) and dried it out completely. It turned greyish,blue and was grainy and dry

Reaction 4: We added water to the anhydrous salt! Remember what happens:??? You get the hydrate back.

Reaction 5: We took 2 test tubes, one contained CaCl2(l) and the other Na2CO3(l) and we poured the calcium chloride into the sodium carbonate.

Reaction 6: We took mossy, fuzzy zinc and submerged it in hydrochloric acid.

Reaction 7: Manganese (IV) oxide is added to hydrogen peroxide. We tested the gas by placing a burning splint into the test tube. It lit up!

http://www.youtube.com/watch?v=ARRCD_Ry4eI  #1
http://www.youtube.com/watch?v=oQz5YEsx7Fo #6

Sorry we couldn't find them all!

More Chemical Reactions

Today we learned about three more types of chemical reactions.
These were Combustion, Neutralization and Double Replacement.

Combustion: A process where a substance reacts with oxygen 

 The formula looks like this: AxBy + O2 -------> AO + BO

Here is an example of an equation which is a combustion reaction

__C7H6O2 + __O2(g) ----> ___CO2(g) + __H20 (l)

As you can see, a compound reacts with oxygen to produce carbon dioxide and water.

Now if we were to balance this it would look like:

2 C7H6O2 + 15 O2(g) -----> 14CO2(g) + 6 H2O(l)

Double Replacement:
This reaction is similar to single replacement except that it involves two compounds and either both non metal or metal compounds trade places:

AB + CD ------> AD + CB

Eg. Na2CO3 + CaCl2--> CaCO3 + 2NaCl
This is the balanced equation for a double replacement reaction:
As you can see,  the carbonate CO3 and the Chloride exchanged places .




Neutralization: This occurs in acid and base interaction , they cancel each other out = neutralization

HA + BOH ----> H2O + BA

The product is water and a salt.

Here is an example:

H2SO4 + Fe(OH)2-----> H2O + FeSO4
Balance:  1 H2SO4 + 1 Fe(OH)2 ----> 2H2O + 1 FeSO4



Here are some helpful videos http://www.youtube.com/watch?v=tE4668aarck
Here is a video that demonstrates combustion :http://www.youtube.com/watch?v=2wIz0oIZWZk