Ch 11.2 Types of Chemical Rx Objective

Classifying Rx 5 types of Rx Combination, decomposition, single- replacement, double-replacement, combustion Some Rx do not fit into the 5 categories, some Rx fit into two simultaneously…

Combination Rx Def: Two or more reactants react to form a single new substance H 2 + S → H 2 S

Decomposition Rx Def: A single reactant breaks apart into two or more Products HgO → Hg + O 2 (this is unbalanced !!)

Single Replacement Rx Def: One element replaces an element in a compound K + H 2 O → KOH + H 2 (this is unbalanced!) One hydrogen in water was replaced by K

Double Replacement Rx Two elements switch places Na 2 S + CdNO 3 → CdS + NaNO 3 (this is unbalanced!) S and NO 3 trade places

Combustion Rx Always involves Oxygen as a reactant, often producing light/heat, often producing CO 2 C 8 H 16 + O 2 → CO 2 + H 2 O (this is unbalanced!) S + O 2 → SO 2 (Number of carbons equals number of CO 2 ) Note: Combustion Rx labeling overrides other labeling that would also work…combination Rx, replacement Rx…

Practice 1--balance and name Rx type Solid Magnesium reacts with oxygen gas to form magnesium oxide 1/2:__Mg (s) + __O 2 (g) → ___MgO (s) 3: 1Mg, 2O 1Mg, 1O 1/2: :__Mg (s) + __O 2 (g) → 2 MgO (s) 3: 1Mg, 2O 2Mg, 2O 1/2: : 2Mg (s) + __O 2 (g) → 2 MgO (s) 3: 2Mg, 2O 2Mg, 2O balanced Type: Combustion

Practice Q: When mercury(II) oxide is heated it turns into liquid mercury and oxygen gas 1/2: ___HgO (s) → __Hg (l) + __O 2 (g) 3: 1Hg, 1O 1Hg, 2O 1/2: 2HgO (s) → __Hg (l) + __O 2 (g) 3: 2Hg, 2O 1Hg, 2O 1/2: 2HgO (s) → 2Hg (l) + __O 2 (g) 3: 2Hg, 2O 2Hg, 2O balanced Type: Decomposition Rx

Practice Q: solid potassium reacts with water to form potassium hydroxide (KOH) and hydrogen gas 1/2: __K (s) +__H 2 O → __KOH + __H 2 (g) 3: 1K, 2H, 1O 1K, 3H, 1O 1/2: __K (s) +2H 2 O → __KOH + __H 2 (g) 3: 1K, 4H, 2O 1K, 3H, 1O 1/2: __K (s) +2H 2 O → 2KOH + __H 2 (g) 3: 1K, 4H, 2O 2K, 4H, 2O 1/2: 2K (s) +2H 2 O → 2KOH + __H 2 (g) 3: 2K, 4H, 2O = 2K, 4H, 2O balanced! Type: Single Replacement Rx