Intro to Chemical Reactions Chapter 6

How do you know if a chemical reaction occurred? We look for visual signs OR a chemical change -If something bubbles, changes color, forms a solid (precipitate) or combusts the system has underwent a chemical change a new product exists.

Classifying reactions In every reaction we have reactions and products Reactants- are the chemicals present in the system Products- are chemicals formed by the system

Types of Chemical reactions Synthesis reactions- -2 or more chemicals combine to form a more complex product -A + B  AB -Examples: -The formation of potassium chloride from potassium and chlorine gas: -2K (s) + Cl 2 (g)  2KCl

Reaction Types Cont… Decomposition: A compound is broken down into smaller chemical species AB  A + B Examples: 2KCl  2 K (s) + Cl 2 (g) 2H 2 O  2H 2 + O 2

Reaction Types Cont… Single Replacement (aka substitution reaction)- One element being replaced by another element to form a compound. A + BC  AC + B Examples: 3 Ag NO 3 (aq) + Al (s)  Al (NO 3 ) 3 (aq) + 3 Ag (s) Zn + 2HCl  ZnCl 2 + H 2

Reaction Types Cont… Double Replacement- 2 elements are being replaced to form 2 new compounds AB + CD  AD + CB Examples: AgNO 3 + NaCl  AgCl + NaNO 3 SiO 2 + 4HF  SiF 4 + 2H 2 O

Reaction Types Cont… Combustion- A hydrocarbon usually reacts with oxygen to form carbon dioxide and water Hydrocarbon + Oxygen (O 2 )  CO 2 + H 2 O Examples: CH 4 + 2O 2  CO 2 + H 2 O 2C 2 H 6 + 7O 2  4 CO 2 + 6H 2 O

Practice problems: When solid ammonium nitrite is heated, it produces nitrogen gas and water vapor NH 4 NO 2  N 2 + 2H 2 O

Practice Problems Gaseous nitrogen monoxide decomposes to produce di nitrogen monoxide gas and nitrogen dioxide gas 3NO  N 2 O + NO 2

Practice Problems Solid mercury oxide decomposes to produce liquid mercury metal and gaseous oxygen 2HgO  2Hg + O 2

Practice Problems Solid carbon reacts with gaseous oxygen to form gaseous carbon dioxide C + O 2  CO 2

Practice Problems Solid zinc is added to an aqueous solution containing dissolved hydrogen chloride to produce gaseous hydrogen that bubbles out of the solution and zinc chloride that remains dissolved in the water Zn + 2HCl  ZnCl 2 + H 2