Different Types of Chemical Equation Part II

Hi, We are back.

Today we are going to talk about the other types of chemical equation:

• Double replacement
• Combustion
• Neutralization

Double replacement:

Before we talk about chemistry stuff, imagine a school prom. (even though there is practically no dances in Magee...)

Let's say that Bill and Becca are partners and Jack and Jill are partners.

After few rounds of dancing, they decide to switch partners

So Bill dances with Jill and Jack dances with Becca

This situation basically outlines the double replacement reaction in chemistry.

The general formula is:

AB + CD → AC + BD

Note:

There are situations in double replacement where there is a reaction or not.

The key is very simple:

If there is a change in state, (e.g. aqueous to solid) there is a reaction. If there is no change, there is no reaction.

Use the table of solubility determine the states

Next:

Combustion:

This is a reaction where burning with oxygen is involved. In my opinion, I think that this is the easiest.

Basically, when the reactants are organic (carbon, oxygen and hydrogen), the outcome will always be

carbon dioxide and water.

So the formula is

AB + O2 → AO + BO

Lastly,

Neutralization:

This is a special type of double replacement. This deals with only acids and bases.

This is also very simple,

the product will be water and the aqueous solution from metal and non-metal from the acid and base.

So the formula becomes:

HA + BOH → H2O + BA

H and OH are from acids and bases

This is it for today.

Stay tuned for more :D

Different Types of Chemical Equation Part I

Hello,

Today, I am going to talk about different types of chemical equations.

There are 6 in total:

• Synthesis
• Decomposition
• Single Replacement
• Double Replacement
• Neutralization
• Combustion

 Today, We are going to talk about the first 3.

First,

Synthesis equation means that you are adding two or more elements to make one product

For example:

If you add red and yellow, the product will be an orange colour.

In chemistry, take Sodium and Chlorine for example

Sodium plus Chlorine will produce sodium chloride

Na + Cl2 → NaCl

From this we can make a general conclusion:

A + B → C
      or
A+ B → AB

Next,

Decomposition is the exact opposite of synthesis.

For example:

Purple can be broken to red and blue

In relation to chemistry,

MgCl2 → Mg + Cl2

This means that magnesium chloride will produce Magnesium solid and Chlorine gas.

From this we can form a general formula:

AB → A+B

C   → A+B

Next,

Single replacement is when a compound and another reactants switch "partners".

For example,

Lets say Bob, Jill and Jack when to a prom.

For one song, Bob and Jill are dancing, Jack is dancing alone.

For the next song, Jill and Jack are dancing while Bob is dancing alone.

Back to chemistry:

In the equation,

MgCl2 + Na → NaCl + Mg

In this case, Mg and Na switched spots.

There is another case where there is 2 non-metals instead of 2 metals like the equation before.

It would look like this:

NaCl + Br2 → NaBr + Cl2

It is exactly the same.

There is a general formula:

AB + C → AC + B

That's it for today, see you later.

Translating Word Equations & Balancing Equations

Hello,

I am just going to go over some basics in how to translate word equations and balance equations.

Translating word equations:

This is a review from last year's science classes, but we'll go over it again.

Ex. aqueous aluminum oxide and sulphuric acid produce water and aqueous aluminum sulphate.

First,

Find all the elements in the periodic table.

Then,

Put the right charges and balance equation.

Note, in word equations like these "and" means "+" sign, "produce" means "→"
Balancing equations

First, make sure the number of atoms are equal in both sides of the equation.

Eg.  MgBr2  + Cl2  →  MgCl2  +  Br2 

You can see in this equation that there are:

 2 atoms of Br

2 atoms of Cl  &

1 atom of Mg

This is important because if it is different for each side, then it goes against the law of conservation of Mass.

In order to do this efficiently, follow these guidelines:

1. Try to balance metal ions. They are easier to deal with.

2. Balance the non-metals.

3. Balance Oxygen, Hydrogen and Carbon last.

 Try some examples on this site:

http://www.cartage.org.lb/en/themes/sciences/chemistry/inorganicchemistry/chemicslformula/Equation/BalancingWorksheet/BalancingWorksheet.htm

I will put up answers next time.

See you later.

Last Mole Conversion... for now

Molar Volume of Gases at STP

(btw, STP = Standard Temperature & Pressure)

Gases expand and contract based on the temperature, therefore, the volume changes.

Basically, the whole lesson talks about how 1 mole of gas at STP occupies 22.4 L  ..

Sooo, let's try an example >>

                        Calculate the volume occupied by 3.4 grams of ammonia ( NH3 ) at STP..

                        Molar Mass = 17 g 

                        3.4 g  x  1 mole    =  0.2 moles

                                      17 g 

                        0.2 moles  x  22.4 L  =  4.5 L of NH3 

Simple, eh ?!!

DILUTION OF SOLUTION

In the previous lesson, we talked about Molarity, now... We are talking about the Dilution of Solution.. ( Super!! ) 

Chemicals are usually shipped in a concentrated mode. So to make it less concentrated, water is usually added!!

In this lesson, we are going to learn to make solutions of any concnetration from a more concentrated source. 

You guys remember the law of conservation of mass, right?? ..... Yeah I didn't think so either..

Basically, the amount of mass enterring a reaction is equal to the amount of mass coming out!! How is this relevant, you may ask? Well , one answer... Moles of a solute are constant, and do not change..

The simple equation for this is derived from the previous lesson 

M1(L1) = M2(L2)

I have ...                                    I need...

         2.00 L    of HCl                          0.8 L

         16.0 M                                      2.0 M

Here comes the magic...

        16 x L1 = 2 x 0.8 

              L1 = 0.100 L

So you add 0.800 - 0.100 = 0.700 L of water to get the concentration you needed ..

THAT'S IT!!
see you next class !!!

MOLARITY OF SOLUTIONS!!

WELCOME BACK..

The first lesson we took on the first day we started school again, was MOLARITY, or Molar Concentration, of solutions.

A solution is a homogenous mixture that normally consists of 

•  a Solute, which is the smaller quantity, and 

•  a Solvent, which is, well, the bigger quantity

Concentration, is the amount of solute in a solution.

Molarity, is the number of moles of solute in one litre of solution. 

The unit for Molarity is the number of moles per

litre, and can be extremely abbreviated (like the 

case of "mole") to   mol / L ..

It can also be an "M"

( must be capitalized )

So basically, the formula for Molarity is this ::

MOLARITY =  moles of solute (mol)  

                volume (L)

So what do you think of this statement? 

A 5 M solution is more concentrated than a 4 M solution.

hmmmmmmm

Take a minute to think about this, and give it the amount of thinkin git deserves... okay, DONE. 

WELL, YEAH OBVIOUSLY.. 

( You get the point now )

So,, let's try some examples then>>

• Eg1--

                   Sea water contains 28.0 grams of NaCl per Litre, 

                   what is the molarity?

                   

                   First, you might want to convert grams to moles. This is the

                   equation now:

                   # of moles =  28.0 g X   1 mole      =    0.479 moles

                                                    58.5 g

                   You already know you have a Litre, so you divide 0.479 by 1 

                   and another minute or two to try to solve this.. Then you will

                   realize you got   0.479 M.

• Eg2--

                   What weight, in grams, of KCl is there in 2.50 Litres 

                   of 0.50 M ??

                   

                   First, get the number of moles by multiplying 0.50 M 

                   & 2.50 L..

                   You will get 1.25 moles

                   Then convert moles to grams through this>>

                   mass = 1.25 moles  X      74.6 g       =   79.2 g

                                                   1 mole

                 

This lesson is actually easy, those two examples is the hardest it can get..

NEVER FORGET YOUR UNITS.. AND ALWAYS SHOW WORK!!! ;)

Percent Composition

Hello!!

We are going to talk about Percent Compositions!!!

(Isn't that what we use to calculate our marks?? you ask.)

Well... Kind of :)

It is actually: percentage by mass of a species in a chemical formula

Imagine a fruit pie that consists of strawberries, blueberries and blackberries.

and try to figure out how much of the pie is strawberry, blueberry or blackberry.

So back to chemistry.

Eg. What is the percentage composition of H^20?

Always assume you have 1 mole.

Total molar mass is 18g/mol

Molar mass of H^2 is 2g

                      O      is 16g

H^2 =  2g/ 18g  *  100%  =  11.1%

0      = 16/18g  * 100% = 88.9%

The results should  add up to 100%.

This is basically percent compositions!

see ya later!