1. The document discusses chemical reactions, including what makes something a chemical reaction, different ways to describe reactions using word equations, chemical equations, and balanced equations. 2. It describes the main types of chemical reactions - synthesis, decomposition, single replacement, double replacement, and combustion reactions - and provides examples of each. 3. Guidelines are given for writing balanced chemical equations, including identifying the reaction type and using coefficients to balance the mass on each side.

1. Chemical Reactions Chapter 11

2. Using Everyday Equations Every minute of the day chemical reactions are taking place both in and around you. What makes something a chemical reaction? A chemical reaction involves one or more substances, the reactants, changing into one or more substances, the products. Reactants Products “ ” means “yields” or “reacts to produce.”

3. Chemical reactions can be described many ways. One is by using a word equation. A word equation is an equation where reactants and products are represented by words. Example: methane + oxygen Word equations, while useful, are cumbersome. To better describe a reaction, writing the formulas is used. A chemical equation uses formulas of reactants (on the left) separated by an arrow from products (on the right). carbon dioxide + water

4. Example: Fe + O 2 (Skeleton equation) - does not indicate the relative amounts of reactants and products Most often symbols are used to describe the state (i.e., gas, solid, etc.) of each substance Fe 2 O 3

5. Balancing Chemical Reactions Coefficients are small whole numbers that are placed in front of the formulas in an equation in order to balance it. A chemical reaction is also described by a balanced equation in which each side of the equation has the same number of each element and mass is conserved.

6. How do you write a balanced chemical equation? To write a balanced chemical equation- First write the skeleton equation. Then use coefficients to balance the equation so that it obeys the law of conservation of mass. What is the Law of Conservation of Mass?

7. Practice __ H 2 + ___ O 2  ___ H 2 O __ SO 2 + ___ O 2  ___ SO 3

8. Try to balance this reaction: __Al(OH) 3 (s) + __H 2 SO 4 (aq)  __Al 2 (SO 4 ) 3 (aq) + __H 2 O(l) Al S H O Al S H O 1 1 5 7 2 3 2 13 12 18 8 2 3 6 2 10 3 12 18

9. Balance these equations __ Mg + __ O 2 -> __ MgO __ KClO 3 -> __ KCl + __ O 2 __ Cu + __ AgNO 3 -> __ Cu(NO 3 ) 2 + __ Ag __KOH + __ H 3 PO 4 -> __ K 3 PO 4 + __ H 2 O 2 Mg + O 2 -> 2 MgO 2 KClO 3 -> 2 KCl + 3 O 2 Cu + 2 AgNO 3 -> Cu(NO 3 ) 2 + 2 Ag 3 KOH + H 3 PO 4 -> K 3 PO 4 + 3 H 2 O Even better… 2 Mg (s) + O 2 (g) -> 2 MgO (s)

10. Types of Reactions There are five types of chemical reactions we will talk about: Synthesis reactions _____________ reactions Single displacement reactions ________________ reactions Combustion reactions You need to be able to identify the type of reaction and predict the product(s)

11. Steps to Writing Reactions Some steps for doing reactions Identify the type of reaction Predict the product(s) using the type of reaction as a model Balance it Don’t forget about the diatomic elements! (BrINClHOF) For example, Oxygen is O 2 as an element. In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

12. 1. Synthesis reactions Synthesis reactions occur when two substances (generally elements ) combine and form a compound. (Sometimes these are called combination or addition reactions.) reactant + reactant  1 product Basically: A + B  AB Example: 2H 2 + O 2  2H 2 O Example: C + O 2  CO 2

13. Practice Predict the products. Write and balance the following synthesis reaction equations. Sodium metal reacts with chlorine gas Na (s) + Cl 2(g)  Solid Magnesium reacts with fluorine gas Mg (s) + F 2(g)  Aluminum metal reacts with fluorine gas Al (s) + F 2(g) 

14. 2. Decomposition Reactions Decomposition reactions occur when a compound breaks up into the elements or in a few to simpler compounds 1 Reactant  Product + Product In general: AB  A + B Example: 2 H 2 O  2H 2 + O 2 Example: 2 HgO  2Hg + O 2

15. Practice Predict the products. Then, write and balance the following decomposition reaction equations: Solid Lead (IV) oxide decomposes PbO 2(s)  Aluminum nitride decomposes AlN (s) 

16. 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)  BaCO 3(s)  Co (s) + S (s)  NH 3(g) + H 2 CO 3(aq)  NI 3(s)  (make Co be +3) Nitrogen monoxide

17. 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 !!)

18. We have looked at several reactions: Fe + CuSO 4  Cu + Fe 2 (SO 4 ) 3 Li + H 2 O  LiOH + H 2 Such experiments reveal trends. The activity series ranks the relative reactivity of metals. It allows us to predict if certain chemicals will undergo single displacement reactions when mixed: metals near the top are most reactive and will displacing metals near the bottom. Q: Which of these will react? Fe + CuSO 4  Ni + NaCl  Li + ZnCO 3  Al + CuCl 2  Cu + Fe 2 (SO 4 ) 3 NR (no reaction) Zn + Li 2 CO 3 Cu + AlCl 3 Yes, Fe is above Cu No, Ni is below Na Yes, Al is above Cu Cu Hg Ag Ca Mg Al Zn Fe Ni Sn Pb H Au Li Na K Yes, Li is above Zn

19. H is the only nonmetal listed. H 2 may be displaced from acids or can be given off when a metal reacts with H 2 O (producing H 2 + metal hydroxide). The reaction with H 2 O depends on metal reactivity & water temp. Q: will Mg react with H 2 O? cold H 2 O hot H 2 O steam acid NR A: No for cold, yes if it is hot/steam Mg + H 2 O  H 2 + ZnCl 2 Complete these reactions: Al + H 2 O(steam)  Cu + H 2 O  Ca + H 2 SO 4  Na + H 2 O  H 2 + Mg(OH) 2 H 2 + Al(OH) 3 H 2 + CaSO 4 H 2 + NaOH Q: Zn + HCl  Cu Hg Ag Ca Mg Al Zn Fe Ni Sn Pb H Au Li Na K

20. All metals will have a specific place in the activity series. For simplicity, only the most common metals are shown. The metals near the top of the activity series are more reactive because their valence electrons are more easily removed. On tests and exams the activity series may appear as K, Na, … Ag, Au; you must remember that K is reactive, Au is not. If the valence of a metal is not indicated in the question, use its most common valence (in bold on your periodic table) to determine the correct chemical formula. Other Activity Series Information

21. Single Replacement Reactions Write and balance the following single replacement reaction equation: Zinc metal reacts with aqueous hydrochloric acid Zn (s) + HCl (aq)  ZnCl 2 + H 2(g) Note: Zinc replaces the hydrogen ion in the reaction 2

22. Single Replacement Reactions Sodium chloride solid reacts with fluorine gas NaCl (s) + F 2(g)  NaF (s) + Cl 2(g) Note that fluorine replaces chlorine in the compound Aluminum metal reacts with aqueous copper (II) nitrate Al (s) + Cu(NO 3 ) 2(aq)  2 2

23. 4. Double Replacement Reactions Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound Compound + compound  product + product AB + CD  AD + CB

24. 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) 2

25. Practice Predict the products. Balance the equation HCl (aq) + AgNO 3(aq)  CaCl 2(aq) + Na 3 PO 4(aq)  Pb(NO 3 ) 2(aq) + BaCl 2(aq)  FeCl 3(aq) + NaOH (aq)  H 2 SO 4(aq) + NaOH (aq)  KOH (aq) + CuSO 4(aq) 

26. 5. Combustion Reactions Combustion reactions occur when a hydrocarbon reacts with oxygen gas. This is also called burning!!! In order to burn something you need the 3 things in the “fire triangle”: 1) A Fuel (hydrocarbon) 2) Oxygen to burn it with 3) Something to ignite the reaction (spark)

27. Combustion Reactions In general: C x H y + O 2  CO 2 + H 2 O Products in combustion are ALWAYS carbon dioxide and water. (although incomplete burning does cause some by-products like carbon monoxide) Combustion is used to heat homes and run automobiles (octane, as in gasoline, is C 8 H 18 )

28. 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  5 6 8

29. Mixed Practice State the type, predict the products, and balance the following reactions: BaCl 2 + H 2 SO 4  C 6 H 12 + O 2  Zn + CuSO 4  Cs + Br 2  FeCO 3 