BalancingBalancingChemical ReactionsChemical Reactions

Also Known As…Also Known As…

How to become theHow to become the

baddest, craziestbaddest, craziest

chemical assassinchemical assassin to walk the planet!to walk the planet!

Types of Chemical EquationsTypes of Chemical Equations There are a few different ways to describe any chemical There are a few different ways to describe any chemical

reaction.reaction. Let’s look at the chemical reaction that describes the Let’s look at the chemical reaction that describes the

decomposition (breaking apart) of water.decomposition (breaking apart) of water.

Word EquationsWord Equations – These equations use the names of the – These equations use the names of the substances involved in the “substances involved in the “reactants reactants products products” format.” format.

Water Water Oxygen gas + Hydrogen gas Oxygen gas + Hydrogen gas

Skeleton EquationsSkeleton Equations – These use the chemical formulas of – These use the chemical formulas of the substances in the “the substances in the “reactants reactants products products” format.” format.

HH22O O O O22 + H + H22

A closer look at the skeleton equation will reveal a problem…A closer look at the skeleton equation will reveal a problem…We have only one oxygen atom going into the reaction, but, We have only one oxygen atom going into the reaction, but, there are two oxygen atoms coming out of the reaction.there are two oxygen atoms coming out of the reaction.

The Law of Conservation of MassThe Law of Conservation of Mass The The Law of Conservation of MassLaw of Conservation of Mass states that states that

the mass of the atoms making up the reactants the mass of the atoms making up the reactants will be the same as the mass of the atoms will be the same as the mass of the atoms making up the products.making up the products.

Atoms can’t be created or destroyed so this law Atoms can’t be created or destroyed so this law basically means…basically means…

““What goes in…must come out!”What goes in…must come out!”

For instance, if a chemical reaction has five For instance, if a chemical reaction has five carbon atoms going in with the reactants – it carbon atoms going in with the reactants – it must have five carbon atoms exiting the reaction must have five carbon atoms exiting the reaction as part of the products.as part of the products.

For this reason, we must “balance” all of our For this reason, we must “balance” all of our chemical equations, because, what goes in…must chemical equations, because, what goes in…must come out!come out!

Balancing ActBalancing Act To balance a chemical equation – you first need a word To balance a chemical equation – you first need a word

equation. Once you have that you can figure out the proper equation. Once you have that you can figure out the proper formulas of the substances involved.formulas of the substances involved.

A A skeleton equationskeleton equation shows a chemical reaction by using just shows a chemical reaction by using just the formulas of the reactants and products. A yield arrow (the formulas of the reactants and products. A yield arrow () ) is also used to show the direction of the reaction.is also used to show the direction of the reaction.

Now balance the skeleton equation by counting atoms and Now balance the skeleton equation by counting atoms and placing the appropriate coefficients in front of the formulas placing the appropriate coefficients in front of the formulas that need adjusting.that need adjusting.

CoefficientsCoefficients are the large numbers in front of a chemical are the large numbers in front of a chemical formula – you can adjust these. The smaller numbers within formula – you can adjust these. The smaller numbers within the formula are subscripts – if you touch these, I know places the formula are subscripts – if you touch these, I know places they will never find your body!they will never find your body!

If both sides have the same number and type of atoms, you If both sides have the same number and type of atoms, you have achieved the pinnacle of chemistry expressionism! You have achieved the pinnacle of chemistry expressionism! You now have a now have a balanced chemical equationbalanced chemical equation..

All work in chemistry usually begins with a chemical equation All work in chemistry usually begins with a chemical equation that has the proper formulas and is balanced properly.that has the proper formulas and is balanced properly.

How To Pass Grade 10 ChemistryHow To Pass Grade 10 Chemistry

Did you use the Did you use the proper formulas proper formulas based on the word based on the word equation provided.equation provided.

Did you add only Did you add only coefficients? I will coefficients? I will snap if you use snap if you use subscripts!subscripts!

Did you go back Did you go back and double check and double check your balancing act?your balancing act?

Practice EquationsPractice Equations

Try to balance the following chemical equations. Remember, Try to balance the following chemical equations. Remember, count one element at a time and think – what goes in, must count one element at a time and think – what goes in, must come out!...or else!come out!...or else!

1.1. MgClMgCl22 ++ FeBr FeBr33 MgBr MgBr22 + + FeCl FeCl332.2. AlBrAlBr33 + + FF22 AlF AlF33 + + BrBr22

3.3. CHCH44 ++ OO22 HH22O O + + COCO22

4.4. NaOH NaOH + + HH22SOSO44 NaNa22SOSO44 + + HH22OO

5.5. HH22O O + + COCO22 HH22COCO33

6.6. Mg(NOMg(NO33))22 + + NaOH NaOH Mg(OH)Mg(OH)22 + + NaNONaNO33

7.7. AlPOAlPO44 + + Mg(ClOMg(ClO33))22 Al(ClO Al(ClO33))33 + + MgMg33(PO(PO44))22

8.8. CC33HH88 + + OO22 COCO22 + + HH22OO

33 2 2 3 3 2 222 3 3 2 2 3 3

22 2 222 2 2

((alreadyalready balancedbalanced))

22 2 222 3 3 2 2

55 3 3 4 4

One Last Reminder!One Last Reminder! You only add coefficients – the big numbers in front. I will You only add coefficients – the big numbers in front. I will

completely lose it if you start throwing around those little completely lose it if you start throwing around those little subscripts like you are some sort of chemistry revolutionary!subscripts like you are some sort of chemistry revolutionary!

THE ENDTHE END