Types of Reactions, Predicting Products

This post is about the types of reactions, and predicting products of those reactions!

There are several types of reactions:
Synthesis, Decomposition, Single Replacement, Double Replacement, Combustion, and Neutralization

SYNTHESIS: A + B --> AB

This is just your simple 1+1 = 2. Add two together!

Example: Fe(s) + O2(g) --> Fe2O3

Don't forget to balance!
4Fe(s) + 3O2(g) --> 2FeO3

Don't forget to include the states! If you are confused, check out the solubility table!

DECOMPOSITION: AB --> A + B

When something decomposes, it breaks up. Decomposers break up stuff! So think about breaking up the compound:

Think of that gross pile of worms to remember decomposition.

Example: 1SO2(g) --> 1S(g) + 1O2(g)

SINGLE REPLACEMENT: AB + C --> AC + B

In single replacement, they switch partners. But there are only 3 different elements: A, B and C. Remember to put metals with non-metals. Do not put metals together with metals or vice versa. That would be wrong!

4Al(s) + 3Pb(NO3)4 (aq) --> 4Al(NO3)3 (aq) + 3Pb(s)

Ready to step it up a notch?

DOUBLE REPLACEMENT: AB + CD --> AC + CB

There are four different elements in this reaction, so switch them up! Again, put metals with non-metals.

2Sr(OH)2(aq) + 1Sn(NO3)4(aq) --> 2Sr(NO3)2(aq) + 1Sn(OH)4(s)

Now I have skipped a bit into the next lesson, but more practice for you guys! Moving on!

PREDICTING REACTANTS

When we know the type of reaction, we can predict the products. Just use the ABCD models that are given above.

Let's try it out:

1Al(s) + 3AgNO3(aq) -->

From looking at this, we can see that there are two elements and one compound. What could this be?!
The key word is the compound. Decomposition would have just one compound, and synthesis would have two different elements that would form a compound on the other side of the arrow.

So what could it be? Single replacement, of course!

Trashcat does not like single replacement.

So, if it is single replacement then lets finish it off!

1Al(s) + 3AgNO3(aq) --> 1Al(NO3)3(aq) + 3Ag(s)

That is it for today!

Good luck on the test, make me proud!

Enthalpy and Energy Calculations

It's the RETURN OF THE MOLE! 

ok in all seriousness now, today we learnt about Enthalpy and how to calculate energy to moles.

Enthalpy: the total Kinetic and Potential Energy of a substance - the "heat content" of a substance.

Chemists are interested in the change in enthalpy in a chemical reaction. 

In an exothermic reaction, the enthalpy goes DOWN. It is converted into heat and released. 

In an endothermic reaction, the enthalpy goes UP. It is absorbed. 

/\H = Hproduct - Hreactant 

To find the total change in enthalpy, you just subtract the reactant from the product. 

In this picture, C is in the place where the change in Enthalpy would normally be. 

/\H = Hproduct - Hreactant 

/\H = 300 - 100 

/\H = 200 kJ

As you should already know, the unit for enthalpy is kJ, or kilojoules. 

Energy to moles: 

Here is a mole map.

Here is a mole map, with the calculations for Energy -> moles.

As you can see, to get from moles to energy, you simply multiply by the number of kilojoules/1 mole. To get from energy to moles, you multiply by 1 mole/number of kilojoules.

Wahooooo

Translating Word Equations and Review of Naming Compounds

Super late post. Oops.
This lesson is pretty basic.
here's an example of a word equation:
Sodium sulfate and barium chloride -> ?


All you have to do is translate this into something that you can balance. You need to turn the words into ions.
Sodium = Na+ 
Sulfate = SO4 (2-)
Barium = Ba(2+)
Chlorine = Cl(-)


So to write this as a chemical equation, you just substitute in the ions where the words are.
Make sure to balance it!

Na2SO4 + BaCl2 -> BaSO4 + 2 NaCl

This is a Double Replacement. In a double replacement, the ionic compounds exchange partners, with positive ions going with negative ions.

Naming Compounds: 
This is actually extremely simple. Here's a small picture example of some completed compounds.

Basically all you have to do is name the compounds. We've all done it before, it's not too hard of a concept!

Here are some more examples. 

i) barium chloride and sodium carbonate

ii) ammonium chloride and silver nitrate 

iii) sodium phosphate and calcium chloride

Now try doing some more examples, except this time instead of translating word equations, name the compounds.

iv) Be2As3

v) TiCl4

vi) CoP

ANSWERS: 

i) BaCl2 + 2NaCO3 -> 2NaCl + Ba(CO3)2

ii) NH4Cl + AgNO3 -> AgCl + NH4NO3

iii) 2Na3PO4 + 3CaCl2 -> Ca3(PO4)2 + 6NaCl

iv) Beryllium Arsenide 

v) Titanium (IV) Chloride

vi) Cobalt (III) Phosphide 

Here's a quick and simple video on naming compounds
Naming Compounds

Good luck!

Endothermic/Exothermic Reactions

All chemical reactions involve changes in energy. Some reactions release energy (exothermic) and others absorb it (endothermic).

Here are some points to remember:

• If a reaction takes less energy to break bonds than it gives off to form bonds, it is exothermic.
• Enthalpy, represented by H, is the heat contained in the system

Okay, now lets get down to the good stuff! Energy diagrams! Now I am a proud graph hater, but it can be straightforward if you pay attention to all the different names. First, lets learn them:

• Energy of reactants = total potential energy of all reactants in the reaction
• Energy of products = total potential energy of all products in the reaction
• Energy of the activated complex = potential energy of the "transition state" between reactants and products.
• Activation energy = the energy that must be added to get the reaction to progress (reactants to activated complex)
• Delta H (there is no delta sign on this computer, sorry!) = change in potential energy during the reaction.

And what is chemistry without formulas? Here are some to keep in mind:

Delta H: Energy of products - energy of the reactants
Energy of activated complex = energy of reactions + activation energy

If the change in enthalpy is negative, it is exothermic. If it is positive, it is endothermic.

Now, onto the graph.
Label the x axis as the reaction progress. (some unit of time)
Label the y axis Potential Energy in kJs.

Want to see what it all looks like?

From this diagram, you can see everything I just talked about! Notice the labels and try to draw your own!

Here are some videos to help you out!

Endothermic Reactions

Exothermic Reactions

Animation on activation energy

Balancing Equations!!

sorry for the late post :S
but YAY for a change we got something easy to do! Balancing Chemical Equations :)
this is review from grade 9 and 10! if you forgot... heres how it goes.

What is a Chemical Equation?

When a chemical reation occurs it can be described as a equation. It shows the chemical that react, called the reactants which are located on the left hand side. Also the chemicals that they produce, called products which are located on the right hand side of the equation. These two sides are seperated by an arrow that indicated the reactants form the product.

The Concept:

Take a look at this chemical word equation:

Ethane + Oxygen  Carbon Dioxide + Steam

This is the writen equation, now you have to translate it to the chemical equation:

C₂H₆ + O₂ CO₂ + H₂O

In this equation notice how neither the Carbon, Hydrogen or Oxygen atoms match from the left hand side to the right hand side? 

Left has: 2 Carbon, 6 Hydrogen, 2 Oxygen

Right has: 1 Carbon, 2 Hydrogen, 3 Oxygen  

This is why we must balance the equation!

Since there are two carbon atoms on the left side, but only one on the right, so we need to put a 2 in front of the carbon dioxide molecule to give two carbons on each side:

C₂H₆ + O₂  2CO₂ + H₂O

Now we will look at the hydrogen atoms. There are six hydrogen atoms on the left side and two on the right side, so now we have to put a 3 on the right hand side so it is equal to the number of hydrogen atoms on the left hand side:

C₂H₆ + O₂  2CO₂ + 3H₂O

Now there are two carbon atoms on each side, and six hydrogen atoms on each side, but the oxygen atoms don't match. There are 2 of them on the left side and 7 on the right side. This is easily solved by multiplying the oxygen molecule on the left side by 3.5 (as 2 x 3.5 = 7):

 

C₂H₆ + 3.5O₂  2CO₂ + 3H₂O

This gives 2 carbons, 6 hydrogens and 7 oxygens on each side of the equation. The equation is balanced, but rather than a decimal just double all the figures in the equation:

2C₂H₆ + 7O₂  4CO₂ + 6H₂O

YAY! now it is balanced :)

As you go on balancing those quations you may come across molecules as being a unit such as:

SO₄ Dont even worry about it, just go on about your business. Treat them the same way!

Also a note:

Watch out for Diatomic Elements which are specific elements that go around in pairs (atom of 2).

they include: Hydrogen(H2), Oxygen(O2), Flourine(F2), Bromine(Br2), Iodide(I2), Nitrogen(N2), and Clorine(Cl2)

So whenever you are writing a chemical equation, always remember, if u come across these elements alone, they come in pairs of 2!

To help you remember these elements just think: HOFBrINCl

 

HERE ARE SOME SEMI HELPFUL VIDEOS! 

http://www.youtube.com/watch?v=RnGu3xO2h74

http://www.youtube.com/watch?v=BVEvvqMGMSc 

Lab 5B: Types of Chemical Reactions

In class we completed Lab 5B dealing with chemical reactions.
I had completed the lab once before in Grade 10, but regardless, it's always good to do things a second time! You catch things you missed the first time.

The first thing you always need to do is wear your safety goggles. Mrs Chen caught me a few times without them and she is right, always safety first!

 During this lab, you get 7 test tubes and complete a reaction in each one. We later determined the chemical equations for the reactions.

Reaction 1: For reaction 1, you adjust a burner flame to high heat, and then using crucible tongs (safety first), you hold a 6 cm length of bare copper wire in the hottest part of the flame for a few minutes.

During this experiment, we were asked to take observations before, during, and after.

In Reaction 1, before attempting anything, we observed that the wire was stiff and copper coloured. During the experiment, part of the wire exposed to the bunsen burner began to glow, there was a slight kink, and it began to turn black. After the experiment, it was black.

We determined the chemical equation for this reaction was 2Cu + O2 --> 2CuO, and classified it as a synthesis reaction.

Reaction 2: In reaction 2, you clean an iron nail with a piece of steel wool so that the surface of the nail is shiny. The nail is then placed in a test tube and copper (II) sulfate is added so half of the nail is covered.
Before, we noticed that the iron nail was brown, and the solution was an intense blue. During, bubbles and a thick layer formed. After, a copper coloured outer coating grew, it was relatively thick and darker in colour.

We determined the chemical equation for this reaction was 1Fe + 1CuSO4 --> 1Cu + FeSO4 and classified it is a single replacement reaction.

Reaction 3: In reaction 3, solid copper (II) sulfate pentahydrate was put in a test tube so that it was 1/3 full. Then, using the test tube clamp, we held the test tube and its contests at an angle away, heated the test tube, and moved it back and forth over a burner flame. We continued heating until no change was observed. Before, the solution appeared to be powdery and sandlike. During, it turned white, steamed, and bubbled. After, it turned completely white on the outside, bubbled, with lots of steam and sizzling sounds.

We determined the chemical equation for this reaction was 1CuSO4 x 5H20 --> 1CuSO4 + 1H2O and classified it as a double replacement reaction.

Reaction 4: In reaction 4, we allowed the test tube and contests from Reaction 3 to cool. We then used a medicine dropper to add 2 or 3 drops of water to the test tube. Before, the appearance was dirty white with blue specks, and dry and hard. During, it became wet. After, the water was absorbing and the appearance was a light colour.

We determined the chemical equation for this reaction was 1CuSO4 + 5H2O --> 1CuSO4 x 5H20 and classified it as a double replacement reaction.

Reaction 5: For this reaction, we filled a test tube 1/4 full with calcium chloride solution. Then we filled a second test tube full with sodium carbonate solution. We then poured the calcium chloride solution into the test tube containing sodium carbonate solution. Before, the solution appeared to be clear. During the reaction it foamed, became a cloudy white, and after it was thicker, gooey and a dirty white colour.

We determined the chemical equation for this reaction was 1CaCl2 + 1Na2CO3 --> 2NaCl  + 1CaCO3 and classified it as a double replacement reaction.

Reaction 6: With this reaction, we placed a piece of mossy zinc in a test tube. Then added hydrochloric acid solution to the test tube until the mossy zinc was completely covered. Before, it appeared to be exactly what it was called - mossy zinc. During, it expanded, bubbled, and turned a grey sandy colour. After, it slightly hardened and condensed, and became a solid.

We determined the chemical equation for this reaction was 1Zn + 2HCl --> 1H2 + 1ZnCl2 and classified it as single replacement.

Reaction 7: For this reaction, a test tube was half filled with hydrogen peroxide solution. Then, a small amount of manganese (IV) oxide was added. We tested the gas by placing a glowing splint into the mouth of the test tube. Before, we observed that the liquid was clear. During the experiment, it foamed up and seperated. After, it bubbled from the middle, steamed with the glowing splint, turned grey at the top (light) and the top resembled a candle wick.

All in all, it was a pretty cool lab! Here are some videos, some that were shown to us by Ms Mak last year, and some I personally recommend!

This is my favourite!
Several reactions, including single and double replacement!
Animations on reactions!
Who doesn't love a little Bill Nye?

Thats it for now! Have a great long weekend!

Ilanna