1. Chapter 10
Chemical Reactions

2. Evidence of Chemical Change
A chemical reaction is a process by which the atoms of one or more substances are rearranged to form different substances.
4 Indicators
Change in color
Change in temperature or energy
Production of a gas
Formation of a precipitate

3. Representing Balanced Chemical Equations
Reactants
Product
Coefficient
Subscript
Physical state
Symbols
Separates two or more products or reactants
Separates reactants from products
(s) Solid (l) Liquid (g) Gas (aq) Aqueous

4. Balancing Chemical Equations
A written chemical equation must abide by the law of conservation of matter
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

5. Examples Na Cl Mg Br

6. Mg Fe Cl

7. 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

8. Strategies Continued
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

9. 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

10. 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.

11. Writing Chemical Equations
Iron combines with oxygen to form solid iron (III) oxide
All metals are represented by their symbol in the periodic table with NO subscripts.
All elemental gases are diatomic (BrINClHOF)
Use your ion table or molecular name to figure out the chemical formula of compounds in your equation
Balance the equation
Note the physical state of each substance in the equation

12. Practice Problem
Aqueous calcium chloride combines with aqueous silver nitrate to form aqueous calcium nitrate and solid silver chloride.

13. Another Practice Problem
Aluminum combines with aqueous hydrochloric acid (HCl) to form aqueous aluminum chloride and hydrogen gas.
Hint: Write the formula for each substance as if it were independent of the other substances in the equation.

14. Chapter 10 Checklist Balancing equations Writing chemical equations
Determining the physical state of reactants and products
Determining reaction type
Predicting products of a reaction
Determining if a reaction will occur
Writing Chemical Equation Quiz – Tuesday 3/24

15. Physical States Atoms Compounds
Metals – All solid except mercury (liquid)
Nonmetals – all gases except bromine (liquid) and iodine (solid)
Compounds
Covalent compounds – usually a liquid or gas, but not predictable
Acids – always aqueous (aq)
Ionic compounds – refer to solubility table
Soluble (dissolves) – aqueous (aq)
Insoluble (doesn’t dissolve) – solid (s)

16. Chapter 10 Checklist Balancing equations Writing chemical equations
Determining reaction type
Predicting products of a reaction
Determining the physical state of reactants and products
Determining if a reaction will occur

17. Using a solubility Table for Ionic Compounds
NaCO3
General Rules Table
Look up the solubility for a compound’s anion
If the substance is insoluble then it is a solid
If the substance is soluble it is aqueous
Check to see if the cation in your compound is in the exception column.
Common Ion
Solubility
Exceptions
CO32-
insoluble
Group IA and NH4+
Final Answer: NaCO3(aq)

18. Determine the physical states
CaSO4
Solid
(NH4)2S
Aqueous
K3PO4
Aqueous
CuC2H3O2
Aqueous

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

20. 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

21. 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

22. Pre-class Question 3/25 Identify the type of reaction
Combustion Decomposition Single replacememt
Synthesis Double Replacement
Identify the type of reaction

23. Chapter 10 Checklist Balancing equations Writing chemical equations
Determining the physical state of reactants and products
Determining reaction type
Predicting products of a reaction
Determining if a reaction will occur

24. Predicting Products of Hydrocarbon Combustion Reactions
With hydrocarbons, the products are always CO2 (g) and H2O(l)

25. Predicting Products of Synthesis Reactions
For Synthesis Reactions
For metals that only form one cation, determine the charge on the ion of each element (metallic and non-metallic) and form a compound from the two ions.
If one of the elements forms more than one cation or 2 nonmetals are combined, the products can only be predicted if the ratio of elements in the compound are given

26. Predicting Products of Decomposition Reactions

27. Predicting Products of Double Replacement Reactions
Rearrangement of cations and anions to form 2 new compounds.
Reaction occurs when a solid or water is produced from aqueous reactants

28. Predicting Products of Single Replacement Reactions
Refer to the activity series chart to determine if the reaction will occur.
Metals replace metals. Nonmetals replace non-metals