Chemical Reactions Chemical Reaction - Study Questions 1. What is a chemical reaction? 2. What is evidence a reaction has occurred? 3. What is a chemical equation? 4. Define reactants. 5. Define products. 6. Define catalyst. 7. What information is found in an equation? 8. What symbols are used to represent the states of matter? 9. What is the meaning of “aq”? 10. How do you indicate a catalyst is being used in a reaction? 11. What is activation energy? 12. What the three things does conservation of matter require of chemical equations? 13. What is the procedure for balancing a chemical equation? 14. Balance the equation for the reaction of magnesium chloride and silver nitrate to form magnesium nitrate and silver chloride. 15. What is a synthesis reaction? 16. How is a combustion reaction related to a synthesis reaction? 17. What type of reaction is an explosion? 18. Compare decomposition and dissociation. 19. What determines whether one metal will replace another in a single displacement reaction? 20. What is the general form of a double displacement reaction? 21. What type of reaction is each of these? 2Na(s) + Cl2(g) → 2NaCl(s) PCl5(s) → PCl3(s) + Cl2(g) 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(l) BaCl2(aq) + H2SO4(aq) → 2HCl(aq) + BaSO4(s) 22. What is the oxidation number of an element? 23. What is the oxidation number of the fluorine ion? 24. What is the sum of the oxidation numbers in a compound? 31. Can a redox reaction form a molecule? Explain your answer.

Types of Chemical Reactions 5 common types of chemical reactions Synthesis Decomposition Single replacement Double replacement Combustion

The 5 Signs of a Chemical Reaction There are five main signs that a chemical reaction has taken place: Light released Temperature change Production of a gas Formation of a precipitate Color change

Are used to represent chemical reactions 2Mg + O2 2MgO Reactants Products An arrow is placed between them to show the direction of reaction.

Synthesis A + B → AB Means “putting together” Two or more substances (elements or compounds) combine to form a single new compound General Form: A + B → AB Examples: 2H2 + O2 → 2H2O 2Na + Cl2 → 2NaCl

Decomposition AB → A + B Opposite of synthesis reactions a single compound reacts to give two or more products General Form: AB → A + B Examples: 2H2O → 2H2 + O2 2NaCl → 2Na + Cl2

Hydrogen Peroxide 2 H2O2 —> 2 H2O + O2

Single Replacement Reactions A reaction in which one element replaces or displaces another element in a compound. General Form: A + BC → B + AC A and B switch places. Example: Zn + CuSO4 → Cu + ZnSO4

Single Replacement Reactions Use the activity series of metals to determine whether the reaction will work or not.

Double Replacement Reactions A reaction in which two soluble ionic compounds react to form a precipitate (or water). General Form: AC + BD→ AD + BC A and B switch places. Example: AgNO3 + NaCl → NaNO3 + AgCl (ppt)

Double Replacement Reactions       Double Replacement Reactions AgNO3(aq) + KCl(aq) ‑‑‑‑> AgCl(s) + KNO3(aq) Use a solubility table to determine if a precipitate is formed.  

Combustion Reactions The burning of a hydrocarbon in the presence of oxygen. Hydrocarbon: organic compound that is composed only of carbon and hydrogen. Examples: gasoline, kerosene, propane

Combustion Reactions CxHy + O2 → CO2 + H2O + heat General Form: The products are usually carbon dioxide, water, and energy in the form of heat.

Combustion Reactions 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)

Combustion Reactions In general: CxHy + O2 → CO2 + H2O Products in combustion are ALWAYS carbon dioxide and water. Combustion is used to heat homes and run automobiles (gasoline is octane, C8H18) (Note: incomplete burning causes some by-products like carbon monoxide = CO)

Type of Reaction Definition ★ Equation Synthesis Decomposition Single Replacement Double Replacement Two or more elements or compounds combine to make a more complex substance A + B → AB AB → A + B Compounds break down into simpler substances Occurs when one element replaces another one in a compound AB + C → AC + B Occurs when different atoms in two different compounds trade places AB + CD → AC + BD Burning of a hydrocarbon in oxygen producing carbon dioxide and water CH + O2 → CO2 + H2O Combustion A = Red B = Blue C = Green D = Yellow

Identifying Chemical Reactions S = Synthesis D = Decomposition SR = Single Replacement DR = Double Replacement C = Combustion ____ HgO → Hg + O2 ____ Mg + O2 → MgO ____ P + Cl2 → P4Cl10 ____ Al2O3 → Al + O2 ____ Cl2 + NaBr → NaCl + Br2 ____ H2 + N2 → NH3

Identifying Chemical Reactions ____ Na + Br2 → NaBr ____ CuCl2 + H2S → CuS + HCl   ____ CH4 + O2 → CO2 + H2O ____ C + H2 → CH4 ____ KClO3  →   KCl  +  O2  ____ C8H18 + O2 → CO2 + H2O   ____ BaCl2  +  Na2 SO4 → NaCl + BaSO4 ____ S8 + F2 → SF6

What types of reaction is it? 1) NaBr + H3(PO4) → Na3(PO4) + HBr 2) Mg + Fe2O3 → Fe + MgO 3) C2H4 + O2 → CO2 + H2O 4) Pb(SO4) → Pb(SO3) + O2 5) NH3 + I2 → N2I6 + H2 7) H2O + SO3 → H2(SO4)