Balancing Equation

Today we are gong to talk about how to make the number of atoms of each kind on the relevant side equal to those on the product side

Here are some rules :
1. balance the atoms which only occur in one molecule on each side
2. balance the whole group
3. dont jump all over an equation
4. in an elemental form

Examples~
1. Al + CuCl2 ----> Al2Cl3 + Cu
step 1 : (4)Al + (3)CuCl2 -----> (2)Al2Cl3 + (3)Cu
step 2 : u should check if the molecules on both sides are equal
(4Al , 3Cu, 6Cl = 4Al , 3Cu, 6Cl)

2. KOH + H3PO4 -----> K3PO4 + H2O
step 1 : (3)KOH + H3PO4 ----> K3PO4 + (3)H2O
step 2 : checking
(3K, 7O, 6H, 1P  = 3K, 7O, 6H, 1P)

Diluting Solutions to Prepare Workable Solutions

We should make solutions of any concentrration from a more concentrated source.

We can make it by a simple equation.

M1V1 = M2V2

Example 1 :

Theres a 40.0mL of 0.400M NaOH solution is diluted to a final volume of 200.0mL, calculate the new concentration.

Let x be the new concentration.

0.400 x 40.0/1000.0 = 100/1000x

                             x= 6.25

The new concentration is 6.25M

Example 2 :

A 0.700M solution is concentrated by evaporation to a reduced final volume of 200.0mL and a molarity of 1.65M. Calculate the original volume.

Let V be the original volume.

0.700V = 200/1000 x 1.65

        V = 2.33
The original volume was 2.33L

Molar Concentration/ "Molarity" Conversation

Molarity is a number of moles of solute in 1 L of solution. We use "M" to denote molar concentration and ift has the units of "moles/L"

E.g. A 100 M solution is MORE concentrated than a 5 M solution.

Formula: Molarity = moles of solute(mol)/ volume of solution(L) aka M = mol/L

We also learned how to calculate the volume. We will learn more about this topic next class