1. Chemical Reactions
Unit 7 Part 1

2. Chemical Equations and Reactions
Chemical equations are used to show chemical reactions.
Indicators of a Chemical Reaction Include:
Change in color (unexpected)
Production/release of a gas (bubbles)
Change in temperature
Exothermic
Endothermic
Formation of a precipitate (solid)

3. Law of Conservation of Mass
Matter cannot be created nor destroyed, it can only change forms.
Chemical equations must ALWAYS be balanced to obey the law of conservation of mass.
Mass has to be the same on both sides of the reaction.
The number of atoms has to be the same for the products and reactants.
What you start with, you must end with

4. Components of a Chemical Equation
Reactants
Listed on the LEFT side of the equation.
Starting substances (ingredients)
Products
Listed on the RIGHT side of the equation.
Ending substances (produced substance)
Arrow  “Yields”
States of Matter
Solid (s)
Liquid (l)
Gas (g)
Aqueous (aq)
Coefficients
Whole number that proceeds the chemical substance (number of moles of the substance)

5. Steps to Follow to Balance Equations
Determine the number of atoms for each element.
Pick an element that is not equal on both sides of the equation.
Add a coefficient in front of the formula with that element and adjust your counts.
Continue adding coefficients to get the same number of atoms of each element on each side.
**Note: LEAVE THE SUBSCRIPTS ALONE! (you cannot change the chemical formula to balance atoms)

6. Coefficients Coefficients go in front of a compound 4H2O
-All atoms in a compound are multiplied by the coefficient
Number of atoms:
Hydrogen-
Oxygen-

7. Practice With Coefficients
*List the amount of each atom in the 4 substances below:
4CH Ni(NO3)2
3NH Ca3(PO4)2

8. Class Examples - Model See hand out for chemical formulas.
Balancing Word Equations: (See additional steps on next slide)
Potassium chlorate  potassium chloride + oxygen
When solid copper reacts with aqueous silver nitrate, the products are aqueous copper (II) nitrate and silver metal.
Nitrogen and oxygen combine to form dinitrogen pentaoxide

9. Steps to Write Equations
When writing formulas don’t forget to look up charges if the compound is ionic!!!
Diatomic Molecules: Always travel in pairs
H.O.F.Br.I.N.Cl. (Dr. HOFINBrCl)
These elements need a subscript 2 after them if they are by themselves!
Once the equation is written, then balance the equation by adding coefficients.

10. Check for Understanding
Balance the following Chemical Equations:
CH4 + O2  CO2 + H2O
Na2O2 + H2SO4  Na2SO4 + H2O2
N2 + H2 NH3
When solid copper reacts with aqueous silver nitrate, the products are aqueous copper (II) nitrate and silver metal.

11. Steps to Follow to Balance Equations
Determine the number of atoms for each element.
Pick an element that is not equal on both sides of the equation.
Add a coefficient in front of the formula with that element and adjust your counts.
Continue adding coefficients to get the same number of atoms of each element on each side.
**Note: LEAVE THE SUBSCRIPTS ALONE! (you cannot change the chemical formula to balance atoms)

12. Steps to Write Equations
When writing formulas don’t forget to look up charges if the compound is ionic!!!
Diatomic Molecules: Always travel in pairs
H.O.F.Br.I.N.Cl. (Dr. HOFINBrCl)
These elements need a subscript 2 after them if they are by themselves!
Once the equation is written, then balance the equation by adding coefficients.

13. Types of Chemical Reactions
Unit 7 Part 2

14. Types of Chemical Reactions – WHY?
Recognizing patterns allows us to predict future behavior.
Weather experts use patterns to predict dangerous storms so people can get their families to safety.
Political analysts use patterns to predict election outcomes.
Similarly, chemists classify chemical equations according to their patterns to help predict products of unknown but similar chemical reactions.

15. Synthesis Reaction A + B AB
Synthesis Reaction: A reaction in which two or more substances combine to form ONE new compound.
A + B AB

16. Examples of Synthesis Rxn
A + B AB Water: H2 + O2 H2O Table Salt: Na + Cl2 NaCl Given the following reactants, predict the products. S8 + O2

17. Synthesis: 2Mg + O2 → 2MgO

18. Decomposition Reactions
Decomposition Reaction: A reaction in which a single compound breaks down to form two or more simpler substances.
AB A + B

19. Examples of Decomposition Rxn
Digestion is a series of decomposition reactions that break down food for fuel for your body.
The production of gasoline is done by “cracking” crude oil where you break down carbon and hydrogen molecules.
Electrolysis of water:
H2O H2 + O2

20. Decomposition: C12H22O11 → 12C + 11H2O

21. Single Displacement Reaction
Single Displacement Reaction: A reaction in which one element takes the place of another element in a compound.
* A more reactive element will take the place of a less reactive element. (see page 286 Table 3)
AX + B BX + A

22. Examples of Single Displacement
Zn + HCl ZnCl2 + H2
Q: In the example above, which element is more reactive?
CuCl2 + Al
Q: In the above example, predict the products.

23. Single Replacement: Cu + 2AgNO3 → Cu(NO3)2 + 2Ag

24. Double Displacement Reaction
Double Displacement Reaction: A reaction where there is an apparent exchange of atoms or ions between two compounds.
AX + BY AY + BX
Indicators of a double displacement reaction:
Formation of a Precipitate (solid)
Formation of a Gas (bubbles)
Formation of Water

25. Example of Double Displacement
The yellow lines on the roads are made from a double displacement reaction.
Pb(NO3)2 + K2CrO PbCrO4 + KNO3

26. Double Replacement: 3CuCl2 + 2Na3PO4 → Cu3(PO4)2 + 6NaCl

28. Combustion Reactions CxHy + O2 CO2 + H2O
Combustion Reactions: A reaction where an organic molecule is combined with oxygen.
CxHy + O2 CO2 + H2O
Oxygen (O2) is a reactant.
CO2 and H2O are produced

29. Example of Combustion Reaction:
Uses for Combustion
Combustion reactions are used in your home everyday in stoves, water heaters, and furnaces.
Example of Combustion Reaction:
2CH O CO H2O

30. Combustion: CH4 + 2O2 → CO2 + 2H2O

31. Practice (in your notes)
Balance and Classify the following chemical reactions:
__Mg + ___HCl ____MgCl2 + ____H2
__C4H8 + ___ O ____CO2 + ____ H2O
___Ca(OH) 2 + ___H2 SO ____CaSO4 + ___H2O
___N2 + ___O ____N2O5

32. Types of Reactions DEMO Activity
LAB Pictures
Feel free to share –
Keys to success-
Be sure your hand is VERY soapy!!
Keep your hand flat
Keep all your fingers together and “tuck your thumb in”
Do NOT move your hand once it is on fire.
Do not forget to SMILE for your picture! 

33. Chemical Equations/Reactions Exam

34. Acid-Base Reactions HX + B(OH) H2O + BX
Acid/Base Rxn: The reactants will include an acid combining with a base. The products will include water and a salt.
HX + B(OH) H2O + BX

35. Acid-Base Reactions The Bronsted-Lowry Definitions
Acid is a proton donor.
Base is a proton acceptor.
An acid-base reaction is often called a neutralization reaction.

36. Examples of Acid/Base Reaction
HCl + Ca(OH)2 H2O + CaCl2
HCN + K(OH) H2O + KCN

37. Ions in Aqueous Solutions and Colligative Properties
Chemistry 1
(Chapter 13)
Ions in Aqueous Solutions and Colligative Properties

38. Questions From Readings
Explain what happens when an ionic substance is dissolved in water. (examples to strengthen response)

39. Dissociation reactions …
AgNO3 
KBr 
BaSO4

40. Questions from Reading
What is a precipitation reaction? How can you determine if the reaction occurs?

41. Precipitate Reactions (ppt)
Precipitate: An insoluble solid compound is formed during a reaction.
Anions are exchanged between two cations.
(This is a double displacement reaction)
To be a ppt. rxn, both must occur:
1. Both reactants must be aqueous (aq)
2. At least one product must be a solid (s)
You MUST include phase labels with your equation. (See solubility table)

42. Predicting Solubility of Compounds
Use a solubility table to determine if a substance is going to be soluble (aqueous) or insoluble (solid) in water
a) Hg2Cl2
b) KI
c) lead (II) nitrate

43. Practice Solubility
5 Minutes!

44. Rules for ppt. reactions
Write a balanced chemical equation.
Use the solubility table to place phase labels to each formula.
If one of the products is a solid and the reactants are aqueous the reaction is classified as a precipitate reaction.
If all of the products are (aq) then the reaction is NOT a ppt rxn and is classified as double displacement.

45. Q: For each of the following decide if a ppt. will occur.
Aqueous solutions of sodium chloride and iron (II) nitrate are mixed.
B) Aqueous solutions of aluminum sulfate and sodium hydroxide are mixed.

46. Check for Understanding
For the following reactions, predict the identity of the precipitate formed. Write the correct formula of the precipitate on the space. If no precipitate is likely, write No Reaction.
BaCl2 and K2SO4 ______________________
CuCl2 and AgNO3 ______________________
(NH4)3PO4 and CaS ______________________
KCl and Ca(NO3)2 ______________________

47. Ionic Equations
Molecular Equation: Chemical equation in which the reactants and products are written as if they were molecular substances, even though they may exist in solutions as ions.
Must include phase labels (s, l, g, aq)
This provides you with the big picture
Example:
Al2(SO4)3(aq)+ 6NaOH(aq) Al(OH)3(s)+ 3Na2SO4(aq)

48. The next 2 types of equations are only completed for precipitate reactions!!!
Complete ionic equation: Shows all the particles in the solution as they realistically exist.
Break apart the aqueous substances into their ions.
Do NOT break apart s, l, or g!!
When writing a complete ionic equation include the Amount, Symbol and CHARGE!

49. Example of a Complete Ionic Equation
Molecular Equation:
Al2(SO4)3(aq)+ 6NaOH(aq)--- 2Al(OH)3(s)+3Na2SO4(aq)
Complete Ionic Equation: Amount, Symbol, Charge

50. Last step for precipitate reaction:
Net ionic equation: Ionic equations that include only the particles that participate in the reaction.
This tells us what substances actually formed something new in the reaction.
Cross out the spectator ions

51. Writing Net Ionic Equation
Molecular Equation:
Al2(SO4)3(aq)+ 6NaOH(aq)--- 2Al(OH)3(s)+3Na2SO4(aq)
Complete Ionic Equation: Amount, Symbol, Charge
2Al+3 + 3SO Na+1 + 6OH Al(OH)3 + 6Na+1 + 3SO4-2
Net Ionic Equation:
What formed during the reaction?

52. One more example of a precipitate reaction
Calcium hydroxide reacts with sodium carbonate to produce calcium carbonate and sodium hydroxide Molecular Equation: Complete Ionic Equation: Net Ionic Equation:

53. Check for Understanding
Why are complete ionic equations more informative than molecular equations for reactions of ions in aqueous solutions?
What is the difference between a complete/total ionic equation and a net ionic equation?
Why are spectator ions left out of the net ionic equation?
What substance is designated with an (s) in the net ionic equation? What state designation do the other substances have?
Why is it necessary to balance the molecular equation before writing the total and net ionic equation?

54. Check for Understanding
Explain the difference between ionization and dissociation.
What determines how much a solute ionizes in solution?
Explain how to tell the difference between a strong electrolyte and a weak electrolyte.

55. Check for Understanding
Explain the difference between ionization and dissociation.
Ionization occurs when ions are formed from the solute particles due to the action of the solvent.
Dissociation occurs when an ionic compound dissolves into ion.
Difference is ionization’s ions are formed from molecular compounds, not ionic compounds.
What determines how much a solute ionizes in solution?
The strength of the solute molecules
The strength of attraction between solute and solvent
Explain how to tell the difference between a strong electrolyte and a weak electrolyte.
The degree of ionization or dissociation is what determines strength of electrolyte, not the amount of solute dissolved.

56. Oxidation Reduction (REDOX) Reactions
Reactions in which one or more electrons are transferred (redox reactions)
Example:
H2(g) + Cl2(g) HCl(g)
Electrons are transferred from the hydrogen to the chlorine.
Recall Rules for Assigning Oxidation States
Remember: The sum of the oxidation states in a neutral compound must equal zero.

57. Oxidation States
Assign oxidation states to each of the atoms in the following compounds:
Hint: Check that oxidation states sum up to the charge on the compound/ion.
CaF2
C2H6
H2O
ICl5
KMnO4
SO42-

58. Practice- Oxidation States
Fe2O3 + 2Al Al2O3 + 2Fe
THE IRON GAINED ELECTRONS. IT HAS BEEN REDUCED.
THE ALUMINUM LOST ELECTRONS. IT HAS BEEN OXIDIZED.
OIL – Oxidation Involves Loss (of electrons)
RIG- Reduction Involves Gain (of electrons)

59. OIL RIG Practice
For each reaction, identify the atoms that undergo reduction or oxidation (and charges). Also, list the oxidizing and reducing agents.
2H2(g) + O2(g) 2H2O(g)
Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s)
2AgCl(s) + H2(g) 2H+(aq) + 2Ag(s) + 2Cl-(aq)