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!!! ;)