1. Chemical Reactions

2. Symbols used in writing reaction equations +Separates two or more reactants or products  Separates reactants from products (s)Solid state (l)Liquid state (g)Gaseous state (aq)Water solution

3. A chemical reaction always has a change in energy either Heat is given off - Exothermic or Heat is used - Endothermic

4. Breaking bonds (overcoming forces of attraction) requires energy, so you have to add heat  endothermic Making bonds gives off energy  exothermic Most chemical reactions are exothermic (happens naturally)

5. Types of Reactions 1.Combustion reactions 2.Synthesis reactions 3.Decomposition reactions 4.Single replacement reactions 5.Double replacement reactions You will need to be able to identify the type of reaction and predict the product(s)

6. Steps to Writing Reaction Equations 1.Identify the type of reaction 2.Predict the product(s) using the type of reaction as a model 3.Balance it! (Law of Conservation of Mass) 4.***Don’t forget about the diatomic elements! (BrINClHOF) Note: In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

7. Combustion Reactions Combustion reactions occur when a hydrocarbon (a compound containing carbon and hydrogen) reacts with oxygen gas.

8. Combustion Reactions In general: C x H y + O 2  CO 2 + H 2 O Products are ALWAYS CO 2 and H 2 O.

9. Combustion Example C 5 H 12 + O 2  CO 2 + H 2 O Write the products and balance the following combustion reaction: C 10 H 22 + O 2 

10. 1. Synthesis reactions Synthesis reactions occur when two substances (generally elements) combine and form a compound. element + element  1 compound Basically: A + B  AB Example: 2H 2 + O 2  2H 2 O Example: C + O 2  CO 2

11. Synthesis Reactions Here is another example of a synthesis reaction

12. For ionic compounds (metal + non-metal) remember to use the elements’ electrical charges when writing the formula For example: Al + O 2  Al 2 O 3

13. Practice Predict the products. Write and balance the following synthesis reaction equations: Sodium metal reacts with chlorine gas Solid Magnesium reacts with fluorine gas Aluminum metal reacts with fluorine gas

14. 2. Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds The opposite of synthesis reactions 1 Compound  Element + Element In general: AB  A + B Example: 2 H 2 O  2H 2 + O 2

15. Decomposition Reactions Another view of a decomposition reaction:

16. Practice Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes Aluminum nitride decomposes

17. Practice Identify the type of reaction for each of the following synthesis or decomposition reactions, and write the balanced equation: N 2(g) + O 2(g)  Co (s) + S (s)  NI 3(s) 

18. 3. Single Replacement Reactions Single Replacement Reactions occur when one element replaces another in a compound. A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-). element + compound  product + product A + BC  AC + B (if A is a metal) OR A + BC  BA + C (if A is a nonmetal) (remember the cation always goes first!) When H 2 O splits into ions, it splits into H + and OH - (not H+ and O -2 !!)

19. Single Replacement Reactions Another view:

20. Single Replacement is also known as oxidation-reduction The transfer of electrons from metals to nonmetals

21. A replacement reaction occurs only if a more reactive element replaces a less reactive element (Never the other way around)

22. Single Replacement Reactions Write and balance the following single replacement reaction equation: Zinc metal reacts with aqueous hydrogen chloride Note: Zinc replaces the hydrogen ion in the reaction

23. Single Replacement Reactions Sodium chloride solid reacts with fluorine gas Aluminum metal reacts with aqueous copper (II) nitrate

24. 4. Double Replacement Reactions Double Replacement reactions involve an exchange of ions between two compounds. A metal replaces a metal and a nonmetal replaces a nonmetal in a compound Compound + compound  product + product AB + CD  AD + CB

25. Double Replacement Reactions Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Example: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  KNO 3(aq) + BaSO 4(s) Remember! Cations are always written first!!

26. Practice Predict the products. Balance the equation HCl + AgNO 3  CaCl 2 + Na 3 PO 4  KOH + CuSO 4 