Chemical Reactions Quantitative Chem Indicators of a Chemical Reaction Indicators of a Chemical Reaction 1. Formation of a solid (called a precipitate) 1
Indicators of a Chemical Reaction 1. Formation of a solid (called a precipitate) 2. Production of gas Indicators of a Chemical Reaction 1. Formation of a solid (called a precipitate) 2. Production of gas 3. Production (or absorption) of heat and light Parts of a Chemical 2Na (s) + Cl 2 (g) è 2 NaCl (s) 2
Parts of a Chemical Reactants è Products 2Na (s) + Cl 2 (g) è 2 NaCl (s) Parts of a Chemical Reactants è Products 2Na (s) + Cl 2 (g) è 2 NaCl (s) é Coefficients é Parts of a Chemical Reactants è Products 2Na (s) + Cl 2 (g) è 2 NaCl (s) é Subscripts 3
Parts of a Chemical 2Na (s) + Cl 2 (g) è 2 NaCl (s)...é.. é... é States of Matter Parts of a Chemical States of Matter: (s) = solid (l) = liquid (g) = gas (aq) = solution Arrows: è means to yield or produce Why do we need to balance a chemical equation? Because matter is not created or destroyed in a chemical reaction! (The law of conservation of matter) The amount of each element remains the same. 4
Determine the number of atoms in each of the following compounds. NaCl: Na Cl K 3 N: K N Al 2 O 3 : Al O Coefficients! 3NaCl: Na Cl 4Al 2 O 3 : Al O Rules for Balancing (Coeff) 1. Start with the most complex element or compound. 2. Balance oxygen last 3. Balance hydrogen second to last 4. If stuck on oxygen, double everything except O 2, then balance. 5. Double-check your work. 5
Diatomic Molecules 1. The Lucky 7: H 2 N 2 O 2 F 2 Cl 2 Br 2 I 2 2. Tetratomic: P 4 ; Octatomic: S 8 Steps to write chemical eqns 1. Write the elements correctly. 2. Write the compounds correctly by balancing their charges (Exception: Type III cmpds) 3. Balance the chemical equation. 3. Classifying Reactions and Predicting Products 6
C 3 H 8 + O 2 CO 2 + H 2 O NaOH Na 2 O + H 2 O H 2 + O 2 H 2 O Zn + 2 HCl H 2 + ZnCl 2 K 2 CrO 4 + Pb(NO 3 ) 2 2 KNO 3 + PbCrO 4 H 2 CrO 4 + Pb(OH) 2 2 H 2 O + PbCrO 4 Examples of Chemical Reactions Type Definition Characteristics Examples Synthesis Decomposition Two or more reactants combine to form a single product. A compound is broken down into two or more simpler substances. A + B à AB Energy ( Δ ) needs to be supplied. Only 1 compound is formed AB à A + B 1. Metallic Hydroxide àmetallic Oxide + H 2 O 2. Metallic Carbonate àmetallic Oxide + CO 2 3. Metallic Chlorate àmetallic Chloride + O 2 4. Oxyacid à Nonmetallic Oxide + H 2 O 5. Binary Compound à2 Elements Classifying Reactions Δ Mg + O 2 à MgO Δ Fe + S 8 à FeS NaOHàNa 2 O + H 2 O Na 2 CO 3 àna 2 O + CO 2 NaClO 3 ànacl+3o 2 H 2 CO 3 à H 2 O + CO 2 2H 2 O à H 2 + O 2 Type Definition Characteristics Examples Single One element Displacement displaces another element from a compound. Double Two aqueous Displacement compounds switch their cations (or anions). AX + Z à AZ + X A + BX à B + AX A cation replaces a cation or an anion replaces an anion. An element and compound are formed AC+BD à BC+AD Two soluble compounds react Forms two compounds where the cations (or anions) switch places. Cu+AgNO 3 àag+cu(no 3 ) 2 2NaBr+Cl 2 ànacl 2 +Br 2 Zn+2HClàH 2 +ZnCl 2 KI + PbCrO 4 à K 2 CrO 4 + PbI 2 AgNO 3 +CuCl 2 àagcl+cu(no 3 ) 2 Fe 2 (SO 4 ) 3 +HClàH 2 SO 4 +FeCl 3 Classifying Reactions 7
Type Definition Characteristics Examples Neutralization An acid reacts with a base to form salt and water.. Combustion An exothermic reaction that takes place between a substance and oxygen. HA+BOHàBA+H 2 O An acid reacts with a hydroxide compound Produces an ionic compound ( salt ) and water C X H Y +O 2 àco 2 +H 2 O (X and Y are integers) A carbon-based substance that reacts with oxygen. Produces carbon dioxide and water. HCl+NaOH à NaCl+H 2 O H 2 SO 4 +NaOH à Na 2 SO 4 +H 2 O H 2 CO 3 +Ca(OH) 2 àcaco 3 +H 2 O CH 4 + 2O 2 à CO 2 + 2H 2 O 2C 4 H 10 +13O 2 à 8CO 2 +10H 2 O 2C 24 H 50 +73O 2 à48co 2 +50H 2 O Classifying Reactions EQ? Two or more reactants combine to form a single product. Reaction 1: Magnesium + Oxygen Δ 2Mg + O 2 à 2MgO Reaction 2: Formation of Iron (II) Sulfide Δ 8Fe + S 8 à 8FeS SYNTHESIS Reaction 3: Formation of Water Δ 2H H 22 + O 2 2 à H2H 2 2. O A + B à AB Picture Energy ( Δ ) needs to be supplied. (on pg 12) Only 1 compound is formed EQ? A compound is broken down into two or more simpler substances. Reaction 1: Carbonation in Soda H 2 CO 3 à H 2 O + CO 2 Reaction 2: Decomposition of Water 2H 2 O à 2H 2 + O 2 DECOMPOSITION Reaction 3: Decomposition of Table Salt NaClO. 2NaClO 3 à 2NaCl + O3O 2 2 AB à A + B Picture 1. Metallic Hydroxide à 2. Metallic Carbonate à 3. Metallic Chlorate à 4. Oxyacid à 5. Binary Compound à (on pg 12) Metallic Oxide + H 2 O Metallic Oxide + CO 2 Metallic Chloride + O 2 Nonmetallic Oxide + H 2 O 2 Elements 8
EQ? One element displaces another element from a compound. Reaction 1: Copper & Silver Nitrate Cu + AgNO 3 à 2Ag + Cu(NO 3 ) 2 Reaction 2: 2NaBr + Cl 2 à NaCl 2 + Br 2 SINGLE DISPLACEMENT Reaction 3: Zn HCl ZnCl Zn + 2HCl à H 2 + ZnCl 2 AX + Z à AZ + X A + BX à B + AX A cation replaces a cation An anion replaces an anion (on pg 12) An element and compound EQ? Two aqueous compounds switch their cations (or anions). Reaction 1: Potassium Iodide + Plumbous Chromate KI + PbCrO 4 à K 2 CrO 4 + PbI 2 Reaction 2: AgNO 3 + CuCl 2 à AgCl 2 + Cu(NO 3 ) DOUBLE DISPLACEMENT Reaction 3: Fe 2 (SO Fe 2 (SO 4 ) 3 + 4 ) 3 +HClàH à 2 SO 4 +FeCl 3 AC + BD à BC + AD Two soluble compounds react (on pg 12) Forms two compounds where the cations (or anions) switch places. EQ? An acid reacts with a base to form salt and water. Reaction 1: Hydrochloric Acid & Sodium Hydroxide HCl + NaOH à NaCl + H 2 O Reaction 2: H 2 SO 4 + NaOH à Na 2 SO 4 + H 2 O NEUTRALIZATION Reaction 3: HH 2 CO 2 CO 3 + 3 +Ca(OH) 2 à àcaco 3 +H 2 O HA + BOH à BA + H 2 O An acid reacts with a hydroxide compound (on pg 12) An ionic compound ( salt ) and water 9
EQ? An exothermic reaction that takes place between a substance and oxygen. Reaction 1: Candle Experiment 2C 24 H 50 + 73O 2 à 48CO 2 + 50H 2 O Reaction 2: CH 4 + 2O 2 à CO 2 + 2H 2 O COMBUSTION Reaction 3: C 3 CH 3 8 H+ 8 + 5O O 2 à 3CO 2 + H4H 2 O 2. O C X H Y + O 2 à CO 2 + H 2 O (X and Y are integers) A carbon-based substance that reacts with oxygen. (on pg 12) Produces carbon dioxide and water. 10