Advanced Double Replacement

A double replacement is a reaction between two ionic compounds usually in solution.
Today we are going to look further in double replacement.

How can we determine if a double replacement reaction actually occurs?  If the reactants change state during the reaction, there is a reaction occuring, usually a precipitate forming.  However, if there is no change of state, then there is no reaction.

We can use the Table of Solubility to determine the states - aqueous (aq) or solid (s).

There is a NET reaction when you have a precipitation that occurs.  The aqueous ions that are the same on both sides get cancelled.

Balancing Equation

Today, we have went into a whole new chapter that is talking about balancing equations.
I can clearly remember I have seen these kind of equation when I was in Grade 10.

Well, the sole aim of this chapter is to teach you when two or more atoms or compounds react together which is called the reactant and form a new set of compounds on the other side of the equation called the product.

NOTE : the number of atoms of each kind on the reactant side=those on the product side.
              e.g. Ca + Cl2 ---> CaCl2

Now it is your turn to balance the equation by yourself!
Have fun!

Types of Reactions

There are 6 types of chemical reactions that we have learnt today that are listed below,

- Synthesis: GF: A+B ----> C

- Decomposition: GF: A----> B+C

- Single Replacement: GF: A+BC----> BA+C

- Double Replacement: GF: AB+CD---->CB+AD

- Combustion: GF: AB+O2---->AO+BO

- Neutralization: GF: HA+BOH----> H2O+BA

More Advanced Neutralization Reaction:

We have also learnt: Predicting Single Replacement Reactions.

When doing a single replacement equation, you need to concern about what type of elements is more reactive than the other ones because if a non-metal combines with a more reactive metal, when it replaces with a less reactive metal, the reaction will not occur.

Molar Volume at STP

                                    Today in Class we leart about molar volume. 


What is molar volume?
molar volume is  gas at Standard Temperature and Pressure(STP) is 22.414 L/mol.


Ex: Find the Volume occupied by 3.00 mol of NO2 at STP
Ans: 3.00 NO2*22.4L/1mol =67.2L of NO2




LOOK IS A MOLE BALL IN STP!!!!

 

This is How to Convert From Moles to STP and from STP to Moles!!!

Ex: find the number of moles in 187.04L of nitrogen gas(N2) at 0 degrees and 101.3kPa


Ans:187.04L N2*1mol/22.4L=8.35 mol N2
 (The L cancels and you get Mol!!!)

Diluting Solutions to Prepare Workable Solutions

Today we've learned the dilution calculation.  For example, if I have a 2 L of 16 M solution, but all I need is a 0.8 L of 2 M solution, how can I diluted the more concentrated solution into the less concentrated one?

First of all
assume:-initial concentration of solution=M1
               -initial volume of solution=L1
               -diluted concentration=M2
               -diluted volume=L2

                     mol
Since M = ---------         
                      L

then  mol = M x L
which means   moles of chemical in concentrated solution = mole concentrated = M1 x L1
and                   moles of chemical in diluted solution = mole diluted = M2 x L2

But the amount of the chemical is not changed when the solution is diluted, only the concentration of the chemical is changed.
Therefore          moles of concentrated chemical = moles of diluted chemical
                                                            OR
                                               M1 x L1 = M2 x L2
So, 16 M x L1 = 2 M x 0.8 L
       16 M x L1 = 1.6 mol
        L1 = 1.6 mol / 16 M
        L1 = 0.1 L
If I need 0.1 L of the 16 M solution to make 0.8 L of 2 M solution......
I would take 0.1 L of the concentrated solution and add how much water?

     0.8 - 0.1 = 0.7 L

Molar Concentration or "Molarity" of Solutions

Today we have learnt about Molar Concentration, is the numbers of moles of solute in one Litre of a solution. We use "M" (always capitalized) to denote molar concentration and it has the units of mols/L.

The formulae is:
                  moles of solute (mol)
Molarity=------------------------------------
                  volume of solution (L)
                         mol
or simpler M=----------
                         L

Here's a clip about how to calculate mole~





Calculating the Empirical Formula of Organic Compound

Today we've learned how to calculating the empirical formula of organic compound, well, it is sort of complicated, but if you follow step by step you will find out it is not hard at all !!

So, to get started, lets know what is an organic compound.
-An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon.

The empirical formula of an organic compound can be found by:
-Burning the compound
-Collecting and weighing the products
-From the mass of the products, the moles of each element in the original organic compound can be calculated


Ex. What is the empirical formula of a compound that when a 5.00 g sample is burned produces 15.0 g of CO2 and 8.18 g of H2O?

First let the empirical formula of the compound be CxHy
CxHy  +  z  O2  =  x  CO2  + y/2  H2O

We want to find x and y (the simplest ration of the atoms or moles of the elements).
From the equation above, we can see that ALL of the C and the H in CxHy went into making x CO2 and y/2 H2O

mol CO2  = 15.0 g CO2  x 1 mol CO2 / 44.0 g CO2 = 0.341 mol
mol H2O =8.18 g H2O x 1 mol H2O / 18.02 g H2O = 0.454 mol

0.454 moles of water and 0.341 moles of Carbon dioxide were produced

mol C = 0.341 mol CO2 x 1 mol C / 1 mol CO2 = 0.341 mol  C
mol H = 0.454 mol H2O x 2 mol H / 1 mol H2O = 0.908 mol H 

Divide both by the smallest molar amount 

Carbon  0.341 / 0.341 = 1
Hydrogen  0.908 / 0.341 = 2.66


Scale ratio to whole numbers


2.66 x 3 = 8  H
0.341 x 3 = 3  C


   C3H8