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 + H2O

Continued

• 2. Gas given off• Ex: hydrochloric acid plus aluminum• HCl + Al AlCl3 + H2

• Ex: Vinegar plus baking soda• CH3COOH + NaHCO3 CH3COONa

+ H2CO3

• H2CO3 H2O + CO2

Continued

• 3. Formation of precipitate (ppt), (solid)

• Ex: potassium iodide plus Lead nitrate• Pb(NO3)2 + 2 KI ==> PbI2¯ + 2 KNO3

Indicators of Chemical RXNS

• 4. Heat or light given off• Methane + Oxygen + Heat

• CH4 + 2 O2 → CO2 + 2 H2O 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 H2O

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• H2, N2, O2, F2, Cl2, Br2, I2

continued

3. Law of conservation of mass must be satisfied.

• This is done by balancing equations• How are equations balanced???• COEFFICIENTS

• 2H2 + O2 2H2O

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 1st

• Next, Balance nonmetals other than H and O• Balance H• Save O for last• www.mmschemistryclass.weebly.com

PagesChapter 8Rx 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 O2 to form oxides• 2Mg + O2  →  2 MgO• 4Fe + 3O2 → 2 Fe2O3

• C(s) + O2(g) → CO2(g)

Synthesis cont. A + B → AB

• Oxides plus water• CaO(s)+ H2O(l) → Ca(OH)2(s)

• SO2(g) + H2O(l) → H2SO3(aq)

• Metals with Halogens• 2Na(s) +Cl2(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:

• 2H2O(l) 2H2(g) + O2(g)

• Some Oxides will Decompose:• 2HgO(s) 2Hg(l) + O2(g)

Decomposition Cont. AB → A + B• Metal carbonates + Heat

• CaCO3(s) CaO(s) + CO2(g)

• Metal Hydroxide + Heat• Ca(OH)2(s) CaO(s) + H2O(g)

• Decomposition of Acids• H2CO3(aq) H2O(l) + CO2(g)

• H2SO4(aq) H2O(l) + SO3(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(NO3)2(aq) → 2Al(NO3)3(aq) + 3Pb(s)

• Metal replaces H2 in H2O or an Acid

• 2Na + 2H2O → 2Na(OH) + H2

• Mg(s) + 2HCl(aq) → MgCl2(aq) + H2

• Halogen by a Halogen• Cl2(g) + 2KBr(aq) → 2KCl(aq) + Br2(l)

• Br2(l) + KCl(aq) → No Rx

Examples• Basically:

– →

• Practice:• Magnesium + HCl• Calcium + HCl• Zinc + H(NO3)

• Iron(II) + AlCl3

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(NO3)2(aq) + 2KI(aq) → 2KNO3(aq) + PbI2(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 CO2 and H2O

Balancing Quiz

• 1. __Al2(SO3)3 +__Na(OH) __Na2(SO3) +__Al(OH)3

• 2. __P4O10 + __H2O __H3PO4

• 3. __KClO3 __KCl + __O2

• 4. __NH4NO3 __N2O + __H2O

Review p.p. 290-292

• # 14, 15, 22, 23, 24, 25, 27