1. Chemical Reactions and Equations
Chapter 6
Chemical Reactions and Equations

2. Warm-up 2/4
Who can recall what the 4 pictures were on the intro slide for this chapter?
Fire
Two flasks (one with a blue liquid and one with a yellow liquid)
Test tube with a blue solid substance
Smoke trail
What do all of these things have to do with chapter 6?
They all show signs of a chemical change

3. Indications of a Chemical Change
The change of one or more substances into new substances by the rearrangement of atoms.
4 𝐹𝑒 (𝑠) + 3𝑂 2(𝑔) →2 𝐹𝑒 2 𝑂 3(𝑠)
Indications of a Chemical Change
Change in energy
Change in color
Formation of a gas
Formation of a Precipitate
(two liquids combine and a solid is produced)

4. Parts of a Chemical Equation+ → 𝐹𝑒 3
𝑂 2 2
𝐹𝑒 2 𝑂 3 4
(𝑠)
(𝑔)
(𝑠)
Reactants
Products
Coefficients
Physical States
(solid, liquid, gas or aqueous)

5. Writing Equations Word Equations
Using the names of chemicals to describe chemical reactions
𝑠𝑜𝑙𝑖𝑑 𝑠𝑜𝑑𝑖𝑢𝑚+𝑐ℎ𝑙𝑜𝑟𝑖𝑛𝑒 𝑔𝑎𝑠→𝑠𝑜𝑙𝑖𝑑 𝑠𝑜𝑑𝑖𝑢𝑚 𝑐ℎ𝑙𝑜𝑟𝑖𝑑𝑒
Chemical Equations
Using chemical formulas and numbers to describe chemical reactions
2 𝑁𝑎 (𝑠) + 𝐶𝑙 2(𝑔) →2𝑁𝑎 𝐶𝑙 (𝑠)

6. Practice Problems Use your ion tables
Re-write the following chemical equation in words
Re-write the following word equation as a chemical equation
Solid copper + fluorine gas = solid copper (II) fluoride

7. Energy
When chemical reactions take place, energy is either absorbed or released in the process
An endothermic reaction
2 𝐻 2 𝑂 (𝑙) +𝒆𝒏𝒆𝒓𝒈𝒚→2 𝐻 2(𝑔) + 𝑂 2(𝑔)
An exothermic reaction
𝐶𝐻 4 (𝑔) + 𝑂 2(𝑔) →𝐶 𝑂 2(𝑔) +2 𝐻 2 𝑂 (𝑙) + energy

8. Watch the following video to complete the warm up
Write the following chemical equation for the reaction that occurred in the video:
Aluminum + iodine = aluminum iodide
You should be able to answer the following questions:
What are the reactants?
What are the products?
What was the indication that a chemical change took place?
Was this an endotherm or exothermic reaction?

9. Physical States of Elements
Metals
Metals are always represented by their symbols from the periodic table, with no subscripts
All metals, with the exception of mercury are solid and will have an (s) following their symbols in an equation
Cu(s)
Non-metals
Are often diatomic (Br,I,N,Cl,H,O,F) so they will have a subscript of 2.
Most of these diatomic elements will be a gas except iodine (s) and bromine (l)
Cl2(g)

10. Physical States of Ionic Compounds
Their physical state will be
(aq) = aqueous if they can dissolve in water
(s) = solid if they can’t
Use this table to determine the solubility of ionic compounds:

11. More Practice Problems
What would be the physical states of the following substances if written in a chemical equation?
PbI2 __________ KNO ____________
KI __________ Pb(NO3)2 ____________
Write the following equation with physical states:
Lead (II) nitrate combines with potassium iodide to form potassium nitrate and lead (II) iodide.

12. Warm-up 2/8 Write the chemical equation for the reaction:
(Use a solubility table to predict the physical states of each compound)
potassium iodide + lead (II) nitrate = potassium nitrate and lead (II) iodide
Watch the following video to see what happens
Did you write the correct physical state for each compound in the reaction?

13. Balancing Chemical Equations
Why?
To demonstrate the Law of Conservation of Mass which states:
In a chemical reaction mass is neither created or destroyed
Antoine Lavoisier
What must be conserved?
The number and type of atoms
2 𝑁𝑎 (𝑠) + 𝐶𝑙 2(𝑔) →2𝑁𝑎 𝐶𝑙 (𝑠)
2 sodium atom + 2 chlorine atoms = 2 sodium atoms + 2 chlorine atoms

14. How to Balance a Chemical Equation
Make sure that both sides of an equation have an equal number of each type of atom represented.
Balance equations by adding coefficients.
Never mess with subscripts Na Cl Mg Br

15. Strategies for Balancing Chemical Equations
1. The even/odd combination
Make the subscript of one, the coefficient of the other and vice versa.
Iron (III) oxide Iron + Oxygen
Practice:

16. Strategies Continued Mg OH Al
2. Balance groups as a whole if the elements of the group are only represented in the group on each side of the equation. Mg OH Al
Practice:

17. Strategies Continued 3. Balancing Hydrocarbon Combustion Reactions
The first step is to add a coefficient to the hydrocarbon so that the total number of hydrogens in the molecule is divisible by four. Then, balance the product side of the equation before finishing up with oxygen. C H O
Practice:

18. Strategies Continued
Splitting Water
When hydroxide shows up on one side of an equation and water is on the other side, split water into H(OH) to balance out hydroxide.
Practice:

19. Things to Keep in Mind Again, do not mess with subscripts
In the final solution, the coefficients have to be in the lowest whole number ratio.
If at first you don’t succeed, try, try again! Most of the solutions to these problems come from trial and error.

20. Comprehensive Practice Problem
Write the equation
Note the physical state of each substance
Balance the equation
Potassium chromate combines with lead (II) nitrate to form potassium nitrate and lead (II) chromate

21. Types of Chemical Reactions
5 General Types
Synthesis
Decomposition
Single displacement
Double displacement
Combustion
You will need to know how to identify these reactions

22. Types of Chemical Reactions – 5 General Formulas
Combustion
CxHy + O CO2 + H20
Synthesis
A + B AB (Two elements combine to form a compound)
Decomposition
AB A + B (One compound splits to form two compounds)
Always the products of these combustion reactions

23. Reactions Cont. Single Replacement (Single Displacement)
A + BC AC + B Metals replace metals
Non-metals replace non-metals
Double Replacement (Double Displacement)
AB + XY AY + XB Compounds switch partners

24. Practice Problems Identify the type of reaction
Combustion Decomposition Single replacememt
Synthesis Double Replacement
Identify the type of reaction