CHEMICAL REACTIONS CHAPTER 8

Answer this in your own words. What is a chemical reaction? How do you know a chemical reaction has Occurred?

Continued 1. Color change Ex: copper (II) hydroxide plus heat Cu(OH) 2 + heat  CuO + H 2 O

Continued 2. Gas given off Ex: hydrochloric acid plus aluminum HCl + Al  AlCl 3 + H 2 Ex: Vinegar plus baking soda CH 3 COOH + NaHCO 3  CH 3 COONa + H 2 CO 3 H 2 CO 3  H 2 O + CO 2

Continued 3. Formation of precipitate (ppt), (solid) Ex: potassium iodide plus Lead nitrate Pb(NO 3 ) KI ==> PbI 2 ¯ + 2 KNO 3

Indicators of Chemical RXNS 4. Heat or light given off Methane + Oxygen + Heat CH O 2 → CO H 2 O magnesium plus oxygen

Characteristics of Chemical RXNS 1. Equation must be a true statement Non Ex: sodium plus chlorine produces water Ex: Lithium plus oxygen produces potassium oxide Non Ex: silver plus chlorine produces gold chloride True Ex: H + O  H 2 O

continued 2. The equation must show correct formulas for both reactants and products. Have to use correct nomenclature. Have to account for 7 diatomic molecules If a reaction gives off a diatomic gas you have to show it in diatomic form H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2

continued 3. Law of conservation of mass must be satisfied. This is done by balancing equations How are equations balanced??? COEFFICIENTS 2H 2 + O 2  2H 2 O

Coefficients Have to be whole numbers 2,3,4,5,6,… Can only be placed in front of a compound Cannot be squeezed in between the ions of a compound.

Tips for Balancing Balance metals/polyatomic ions 1 st Next, Balance nonmetals other than H and O Balance H Save O for last Pages  Chapter 8  Rx balancing Practice First Link- Do 5 easy, 10 intermediate, 15 hard (WRITE THEM DOWN AS YOU GO) Second Link-Complete balancing the equations and check your answers. (WRITE DOWN the 5 Hardest to complete correctly)

Write the word equations below as chemical equations and balance: 1) Zinc and lead (II) nitrate react to form zinc nitrate and lead. 2) Aluminum bromide and chlorine gas react to form aluminum chloride and bromine gas. 3) Sodium phosphate and calcium chloride react to form calcium phosphate and sodium chloride. 4) Potassium metal and chlorine gas combine to form potassium chloride. 5) Aluminum and hydrochloric acid react to form aluminum chloride and hydrogen gas. 6) Calcium hydroxide and phosphoric acid react to form calcium phosphate and water. 7) Copper and sulfuric acid react to form copper (II) sulfate and water and sulfur dioxide. 8) Hydrogen gas and nitrogen monoxide react to form water and nitrogen gas

5 Types of Chemical Rxns 1. Synthesis (composition)-two or more substances combine to form a new cpd. A + B → AB Metals, Non-Metals react with O 2 to form oxides 2Mg + O 2 → 2 MgO 4Fe + 3O 2 → 2 Fe 2 O 3 C (s) + O 2(g) → CO 2(g)

Synthesis cont. A + B → AB Oxides plus water CaO(s)+ H 2 O (l) → Ca(OH) 2(s) SO 2(g) + H 2 O (l) → H 2 SO 3(aq) Metals with Halogens 2Na (s) +Cl 2(g) → 2NaCl (s) + → Basically

2. Decomposition Rxn Decomposition Rx- 1 Cpd breaks up into 2 or more elements Most require heat or electricity AB → A + B Simplest: Binary Cpds By electric current: 2H 2 O (l) 2H 2(g) + O 2(g) Some Oxides will Decompose: 2HgO (s) 2Hg (l) + O 2(g)

Decomposition Cont. AB → A + B Metal carbonates + Heat CaCO 3(s) CaO (s) + CO 2(g) Metal Hydroxide + Heat Ca(OH) 2(s) CaO (s) + H 2 O (g) Decomposition of Acids H 2 CO 3(aq) H 2 O (l) + CO 2(g) H 2 SO 4(aq) H 2 O (l) + SO 3(g) – + Basically

3. Single Replacement Rxn Single Replacement Rx- 1 element is replaced by a similar element or cmp. A + BC → AC + B D + BC → BD + C A Metal can replace a metal 2Al (s) + 3Pb(NO 3 ) 2(aq) → 2Al(NO 3 ) 3(aq) + 3Pb (s) Metal replaces H 2 in H 2 O or an Acid 2Na + 2H 2 O → 2Na(OH) + H 2 Mg (s) + 2HCl (aq) → MgCl 2(aq) + H 2 Halogen by a Halogen Cl 2(g) + 2KBr (aq) → 2KCl (aq) + Br 2(l) Br 2(l) + KCl (aq) → No Rx

Examples Basically: –→–→ Practice: Magnesium + HCl  Calcium + HCl  Zinc + H(NO 3 )  Iron(II) + AlCl 3 

4. Double Replacement Rxns Double Replacement Rxs- Two ionic cpds swap ions in aqueous solution Usually get an insoluble ppt, A gas, or a molecualr cmp Ions Swap places: Pb(NO 3 ) 2(aq) + 2KI (aq) → 2KNO 3(aq) + PbI 2(s)

Examples Lead(II)nitrate + potassium Iodide  Aluminum oxide + sodium nitrate  Aluminum sulfate + barium chloride 

5. Combustion Rxns Combustion Rx: Substance combines with O2 and releases a large amount of energy in the form of Light and heat. All produce CO 2 and H 2 O

Balancing Quiz 1. __Al 2 (SO 3 ) 3 +__Na(OH)  __Na 2 (SO 3 ) +__Al(OH) 3 2. __P 4 O 10 + __H 2 O  __H 3 PO 4 3. __KClO 3  __KCl + __O 2 4. __NH 4 NO 3  __N 2 O + __H 2 O

Review p.p # 14, 15, 22, 23, 24, 25, 27