Balancing Equations and Types of Reactions

We balance the number of atoms in the reactant side and the product side to make them equal, but how do we do it?

A beginner's guide to balancing equations by Mr. Anderson!

Watch this as a review for balancing equations from Grade 10 Science.



Types of Reactions
- There are six types of reactions : Synthesis, decomposition, single replacement, double replacement, combustion and neutralization. For now, we will cover the first 3 types of reactions first.

Synthesis
- combines 2 or more reactants to make one product    (A+B ---> C)

eg. 4 Fe + 3 O2 → 2 Fe2O3 
eg. CO2 + H2O → H2CO3

Decomposition- One reactant is broken into 2 or more products (A---> B+C)

eg. 2KClO₃ → 2KCl + 3O₂
eg. 2H₂O₂ → 2H₂O + O₂

Single Replacement.
- an element replaces an ion in an ionic compound
- non-mental elements will replace a negative ion
- mental elements will replace a positive charged ion

eg. Cl₂ + 2NaBr → 2NaCl + Br₂
eg. Zn + 2HCl → ZnCl₂ + H₂

Activity Series

 

- Not all replacement reactions are possible

- This is because some elements are more reactive than another due to the amount of electrons in the outer shell
- If the element that is doing being replaced is lower down in the chart than the one doing the replacing, the replacement is POSSIBLE. Otherwise, the reaction is not possible, meaning that no reaction will occur.

eg. Fe  + CuSO₄  → Cu  + FeSO₄

_{This reaction is possible because iron is higher up on the chart so it's able to knock copper out}

eg. I₂ + 2KBr → no reaction

There will be no reaction because Iodine is not as reactive as Bromide

- Catherine

Lab 4C

 For Lab 4C, "Determining the Empirical Formula of a Compund", we got an unknown hydrate that filled 1/3 of a crucible. We place the crucible on a pipestem triangle with a bunsen burner underneath it; once the crucible turns dull red with heat, we let it cool for around 5 minutes. After weighing it, we heat it once again for approximately 5 minutes and then determine the mass. We reheat it so that we are sure there is no more water left so the hydrate becomes an anhydrous salt.

Molar Volume of a Gas at STP

    Since gases expand and contract depending on the pressure and temperature, we use STP (Standard Temperature and Pressure to make sure all gases are measured accurately. 1 mole of gas is to take up 22 L, at 1 atmostphere of pressure and a temerature of 0°.
   Converting from molà litres
   Ex: Calculate the volume (L) of 20mole of ammonia at STP
       
  20mol x      22.4L             = 448L
                __________
                  1 mole



 Converting from litresà mol
 Ex: Calculate the number of moles in 5.54 L of CO2 at STP

 5.54L x  1 mole         =  0.247 mol
              _________
               22.4 L

-Victoria

Diluting Solutions to Prepare Workable Solutions

A Quick Recap:

Solvent = the liquid that does the dissolving

Solute = the substance which dissolves

Solution = is prepared by dissolving a solute in a solvent.

-         When a solution is diluted more solvent is added to it.

-         The moles of solute is always constant (the only difference is that there is more solvent in the less concentrated solution)

The total number of solutes in the solution remains the same after dilution, but the volume of the solution becomes greater.

Thus we have the equation:

            Moles of solute before = Moles of solute after

M₁V₁ = M₂V₂

Lets try an example:

Concentrated HNO₃ is 15.4 mole/L.  How would you prepare 2.50 L of 0.375 M HNO₃?

M₁V₁ = M₂V₂

15.4 mole/L x V₁  = 0.375 M x 2.50 L

→ Re organize the equation

 V₁  = 0.375 M x 2.50 L

                 15.4 M

V₁ = 0.0609 L

V₁ = 60.9 mL

*Remember Sig Figs

To calculate how much water we need in order to dilute the solution we take our known volume (V₂) and subtract it from V₁.

       2.50 L – 0.0609 L  = 2.44L

So, you would need to add 2.44 L of water to make the equation true.

Youtube Time:

http://www.youtube.com/watch?v=KM2uzc8msas

 By Candace

Molarity Concentration / "Molarity" of Solutions

Molar Concentration

Here's a quick review of a past chapter:

Homogeneous mixture, when one substance is dissolved in another it is called a solution.

• the smaller quantity (being dissolved) is called a solute
• the larger quantity (dissolving) is called a solvent

Ex: sugar in tea
The sugar would be the solute and the tea is the solvent.

Molar Concentration / Molarity is the number of moles of solute in one litre of a solution. We use the letter "M" to represent molar concentration, which has the units of "moles/L"

Formulae:

         - Molarity= moles of solute (mol)
                           volume of solution (L)

         - or put more simply:  M=mol
                                                 L

         - mol= MxL           and           L=mol
                                                            M

      
Check out this link for some more help :)

http://www.youtube.com/watch?v=h0cdLIfus8c

Try a practice problem :

Find the molar concentration of a solution that has 0.310 moles of LiOH² in 1.200 L of solution.

-Lauren