PERIODIC TABLE

TITRATION

WHAT IS TITRATION?

• A titration is a technique where a solution of known concentration is used to determine the concentration of an unknown solution. 
• Typically, the titrant (the know solution) is added from a burette to a known quantity of the analyte (the unknown solution) until the reaction is complete. 
• Knowing the volume of titrant added allows the determination of the concentration of the unknown. 
• Often, an indicator is used to usually signal the end of the reaction, the endpoint.

WHAT APPARATUS & CHEMICALS NEED FOR TITRATION IN LAB?

Chemicals

• Acid
• Base
• Indicator

Apparatus

• Conical Flask
• Burette
• Retort Stand
• White Tile
• Filter Funnel
• Pipette

Technique to use pipette

Titration technique

Color of end-point

Video of the titration technique

Some useful website 

1. http://www.avogadro.co.uk/miscellany/titration/titreset.htm
2. https://www.dartmouth.edu/~chemlab/techniques/titration.html

Matriculation students doing their titration in lab

End Point - Light Pink

SHAPE OF ORBITALS

There are four types of orbitals, known as s, p, d and f orbitals.

s orbitals
s orbitals are spherical in shape

p orbitals
p orbitals are shaped like dumb-bells.

d orbitals
d orbitals are shaped like cloverleaf.

QUANTUM NUMBERS

The quantum mechanic model describes the energy levels of the electrons in three dimensional spaces (orbitals).
There are a set of 4 quantum numbers.

1. Principle Quantum Number (n)
2. Azimuthal Quantum Number (l) or Angular Momentum Quantum Number
3. Magnetic Quantum Number (m)
4. Spin Quantum Number (s)

These quantum numbers describe the energy level of an orbital and define the shape and orientation of the region in space where the electron is most likely to be found.

You can read more about quantum numbers by referring to this website: http://chemwiki.ucdavis.edu/Physical_Chemistry/Quantum_Mechanics/10%3A_Multi-electron_Atoms/Quantum_Numbers

BALANCE CHEMICAL EQUATION

A chemical equation is represent of a chemical reaction using symbols of elements and formula of compounds. It takes practice to be able to write balance equation. There are essentially 2 steps to the process.

1. Write the unbalance equation.

• Chemical formulas of reactants are listed on the left hand side of the equation.
• Products are listed on the right hand side of the equation.
• Reactants and products are separated by putting an arrow between them to show the direction of the reaction. Reactions at equilibrium will have arrows facing both directions.

2. Balance the equation.

• Start by balancing an element that appears in only one reactant and product.
• Once one element is balanced, proceed to balance another, and another, until all elements are balanced.
• Balance chemical formulas by placing coefficients in front of them. Do not add subscripts, because this will change the formulas.

You can check this useful website http://www.webqc.org/balance.php

BALANCE REDOX EQUATION

For more complex redox reaction, use ion-electron method. Follow the steps systematically so that equations become easier to balance.

STEP 1: Write the overall equation

Cr₂O₇^2-  +  Cl^-  ®  Cr³⁺   +  Cl₂      

STEP 2: Devide the equation into two half reactions 

reduction:  Cr₂O₇^2-  ® Cr³⁺         

oxidation:  Cl^-  ®  Cl₂                  

(**you must know which pair undergo reduction and oxidation by counting their oxidation numbers**)

STEP 3: Balance the half equation separately. 

i) balance the element other than oxygen and hydrogen

reduction:  Cr₂O₇^2- ®  2Cr³⁺         

oxidation:  2Cl^-  ®  Cl₂         

ii) balance the oxygen atom by adding H₂O, balance the hydrogen atom by adding H⁺ 

reduction: 14H⁺ + Cr₂O₇^2- ®  2Cr³⁺ + 7H₂O        

oxidation:  2Cl^-  ®  Cl₂         

iii) balance the cherge by adding electrons to the side with the greater overall positive charge.

reduction:  6e + 14H⁺ + Cr₂O₇^2- ®  2Cr³⁺ + 7H₂O 
                           ____+12_____              _____+6_____
        

oxidation:  2Cl^-  ®  Cl2 +  2e  

STEP 4: Balance electrons for both half-reactions

Multiply each half-reaction by an integer, so that number of electrons lost in one reaction equals the number gained in the other reaction.

reduction:   6e + 14H⁺ + Cr₂O₇^2- ®  2Cr³⁺ + 7H₂O 
     

oxidation:  ( 2Cl^-  ®  Cl2 +  2e ) X3
                   6Cl^-  ®  3Cl2 +  6e 

STEP 5: Combine both half equations

Cancelling same species appearing on both sides of the equation.

eduction:   6e + 14H⁺ + Cr₂O₇^2- ®  2Cr³⁺ + 7H₂O      

oxidation:                            6Cl^-  ®  3Cl2 +  6e 
_______________________________________________
Overall: 14H⁺ + Cr₂O₇^2- + 6Cl^-  ®  2Cr³⁺ + 7H₂O + 3Cl2 
____________________________________________________________

STEP 6: Verification

Check the equation to make sure that there are the same number of atoms of each kind and the same total charge on both sides.

MOLE CONCEPT

Definition of mole:

Amount of substances that contains the same number of particles (atoms, molecules, formula units, ions) as the are atoms in exactly in 12 g of C-12.

1 mol contains 6.023 x1023 particles

6.023 x 1023 is known as Avogadro's number (NA)

You can check this website for the mol calculation:
http://extracredit-themolecalculator.blogspot.com/

Another concept map for mole conversion:

From Matriculation Chemistry (6th Edition) by Oriental Academic Publication (OAP), 2013.

SUBATOMIC PARTICLES

An atom is made up;

• PROTON
• NEUTRON
• ELECTRON

PROTON (+ve chanrge) and NEUTRON (no charge) are located in the nucleus, while ELECTRON (-ve charge) are move rapidly around the nucleus of an atom.

PROTON NUMBER (Z)

• Also known as atomic number
• Is number of protons in the nucleus of each atom.
• In neutral atom,
• number of protons = number of electrons

NUCLEON NUMBER (A)

• Also known as mass number
• Is a a total number of protons and neutrons present in the nucleus of an atom
• Nucleon Number = Number of protons + Number of neutrons

ISOTOPES

• Are atoms of the same element, having the same number of protons in their nucleus but different number of neutrons.

ATOMS AND MOLECULES

ATOMS

An atoms is the smallest and basic unit of a chemical element or compound.

Example: Na, Li, Ne

MOLECULE

A unit consist of two or more atoms that are chemically bonded together

• Diatomic Molecules : Cl2 , F2, HCl
• Polyatomic Molecules : H2O, CO2

ELEMENT

A substance that cannot be separated into simpler substance by chemical means. Element consists of only one kind of atom and can exist as atom or molecules. For example Na and Li.