1. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS CHEMICAL EQUATIONS magnesium + chlorine magnesium chloride

2. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS CHEMICAL EQUATIONS Mg(s) + Cl 2 (g) MgCl 2 (s) magnesium + chlorine magnesium chloride REACTANTSPRODUCTS BALANCED EQUATION The Law of Conservation of Matter : atoms are neither created nor destroyed in chemical reactions. (atoms are conserved, but molecules are NOT) (s) = solid; (l) = liquid; (g) = gas/gaseous; (aq) = aqueous aqueous (from Latin “aqua” = water) = dissolved in water

3. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS CHEMICAL REACTIONS COMBINATION DOUBLE REPLACEMENT (METATHESIS) DECOMPOSITIONCOMBINATION SINGLE REPLACEMENT (SUBSTITUTION) DECOMPOSITION NONREDOXREDOX

4. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS REDOX REACTIONS OXIDATION REACTIONS (originally) reactions with oxygen nowadays: - process of giving up electrons (increase of positive charge, i.e./or decrease in negative charge) = an oxydation number increase - loss of hydrogen REDUCTION REACTIONS (originally) process in which oxygen was lost nowadays: - process of gaining electrons (increase of negative charge, i.e./or decrease in positive charge) = an oxydation number decrease During ANY redox reaction electrons are exchanged between atoms and/or ions; some are oxidized others are reduced. rusty ironfire

5. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS REDOX REACTIONS Na Na + + e - Cl + e - Cl - Na + Cl Na + Cl - Mg Mg 2+ + 2e - O + 2e - O 2- Mg + O Mg 2+ O 2- Ca Ca 2+ + 2e - 2F + 2e - 2F - Ca + 2F Ca 2+ F 2 - OXIDIZED REDUCED

6. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS REDOX REACTIONS Na Na + + e - Cl + e - Cl - Na + Cl Na + Cl - Mg Mg 2+ + 2e - O + 2e - O 2- Mg + O Mg 2+ O 2- Ca Ca 2+ + 2e - 2F + 2e - 2F 2- Ca + 2F Ca 2+ F 2 - OXIDIZED REDUCED OXIDATION NUMBERS = O.N. (OXIDATION STATES) Positive or negative numbers assigned to the elements in chemical formulas according to specific set of rules. elements: O.N. = 0 Ia group:O.N. = +1 Iia group:O.N. = +2 hydrogen:O.N. = +1 oxygen:O.N. = -2 O (in peroxides only): O.N. = -1 sum of all atoms in a compoundO.N. = 0 sum of all atoms in polyatomic ionO.N. = ion charge

7. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS REDOX REACTIONS A reducing agent (also called a reductant or reducer ) is the element or compound that reduces another species. In doing so, it becomes oxidized, and is therefore the electron donor. An oxidizing agent (also called an oxidant, oxidizer ) can be defined as either a chemical compound that readily transfers oxygen atoms, or a substance that gains electrons. REMEMBER: electron transfers take place ONLY during formation of ionic compounds. In covalent substances the ELECTRONS ARE SHARED. We just, by arbitrary practice ASSIGN SHARED ELECTRONS to the more electronegative element sharing them. None of the atoms in a covalent molecule acquire a net charge.

8. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS DECOMPOSITION REACTIONS 2H 2 O 2 2H 2 O + O 2 (g) CaCO 3 (s) CaO (s) + CO 2 (g) DECOMPOSITION REACTION: A single substance reacts to form two or more simpler substances. Aragonite Calcite Vaterite or (μ-CaCO 3 ) Chalk Limestone Marble Travertine 500 milligram calcium supplements made from calcium carbonate 2HgO(s) 2Hg(l) + O 2 (g) Montroydite

9. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS REPLACEMENT REACTIONS : SINGLE REPLACEMENT REACTION An element reacts with a compound and displaces another element from the compound. COMBINATION REACTIONS : (ADDITION or SYNTHESIS Rxns) Two or more substances react to form a single substance. S (s) + O 2 (g) --> SO 2 (g) 2SO 2 (g) + O 2 (g) --> 2SO 3 (g) SO 3 (g) + H 2 O (l) --> H 2 SO 4 (aq) 2000 United States chemical industry CHEMICAL 2000 PRODUCTION PRODUCTION RANK (in 10 9 kg) 1 Sulfuric acid 39.62 2 Ethylene 25.15 3 Lime 20.12 4 Phosphoric acid 16.16 5 Ammonia 15.03 6 Propylene 14.45 7 Chlorine 12.01 8 Sodium hydroxide 10.99 DOUBLE REPLACEMENT REACTION Two compounds react and exchange partners to form two new compounds. AgNO 3 (aq) + KCl(aq) ‑‑‑‑ > AgCl(s) + KNO 3 (aq)

10. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS IONIC REACTIONS TOTAL IONIC EQUATION NET IONIC EQUATION MOLECULAR EQUATION SPECTATOR IONS Many chemical reactions take place in water. Ionic compounds and some polar covalent compounds DISSOCIATE (break apart) INTO IONS when dissolved in water. 2KI + Pb(NO 3 ) 2 --> 2KNO 3 + PbI 2 (s) 2K + (aq) + 2I - (aq) + Pb 2+ (aq) + 2NO 3 - (aq) --> 2K + (aq) + 2NO 3 - (aq) + PbI 2 (s) 2I - (aq) + Pb 2+ (aq) --> PbI 2 (s) 2K + (aq), 2NO 3 - (aq) HCl(aq) + NaOH(aq) → NaCl(aq) + H 2 O(l) H + (aq) + Cl − (aq) + Na + (aq) + OH − (aq) → Na + (aq) + Cl − (aq) + H 2 O(l) H + (aq) + OH − (aq) → H 2 O(l) Cl − (aq), Na + (aq) NEUTRALIZATION REACTION

11. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS ENERGY and REACTIONS H + (aq) + OH − (aq) → H 2 O(l) ∆H = 13.36 kcalmol -1 NEUTRALIZATION REACTION A + B C + D +/- E (energy) E (energy) released (+) or absorbed (-): heat, light, electricity, motion, high energy chemical bonds HCl(aq) + NaOH(aq) NaCl(aq) + H 2 O(l) + energy HCl(aq) + NaOH(aq) NaCl(aq) + H 2 O(l) ∆H = 13.36 kcalmol -1 EXOTHERMIC REACTION (heat release) ENDOTHERMIC REACTION (heat absorption) C 3 H 8 + 5O 2 ---> 4H 2 O + 3CO 2 + energy propane + oxygen water + carbon dioxide + energy heat, light ("cold-packs.") Combustion reaction

12. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS The MOLE and CHEMICAL EQUILIBRIUM

13. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS The MOLE and CHEMICAL EQUATIONS Stoichiometry is the calculation of quantitative (measurable) relationships of the reactants and products in a balanced chemical reaction (chemicals). Stoichiometry is the mass relationship in chemical reactions. (the math behind chemistry) C 3 H 8 (g) + 5O 2 (g) ---> 4H 2 O(l) + 3CO 2 (g)

14. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS The MOLE and CHEMICAL EQUATIONS Stoichiometry is the calculation of quantitative (measurable) relationships of the reactants and products in a balanced chemical reaction (chemicals). Stoichiometry is the mass relationship in chemical reactions. (the math behind chemistry) C 3 H 8 (g) + 5O 2 (g) ---> 4H 2 O(l) + 3CO 2 (g) 1 mol C 3 H 8 + 5 mol O 2 ---> 4 mol H 2 O + 3 mol CO 2 44 g C 3 H 8 + 160 g O 2 ---> 72 g H 2 O + 132 g CO 2 How many moles and grams of water and carbon dioxide will be obtained if 11 g of propane was burned? 11 g Moles of C 3 H 8 = ------------ = 0.25 44 g Moles of H 2 O = 4 x 0.25 = 1.00 gH 2 O = 1.00 x 18.0 = 18 g Moles of CO 2 = 3 x 0.25 = 0.75 gCO 2 = 0.75 x 44.0 = 33.0 g

15. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS The LIMITING REACTANT LIMITING REACTANT The reactant present in a reaction in the least amount, based on its reaction coefficients and molecular weight. The reactant that determines maximum amount of product that can be formed. LIMITING REACTANT PRINCIPLE The maximum amount of product possible from a reaction is determined by the amount of reactant present in the least amount, based on its reaction coefficients and molecular weight. REACTANT IN EXCESS is the reactant that is not completely used up during the chemical reaction, that is, there is some of this reactant left over. C 3 H 8 + 5O 2 ---> 4H 2 O + 3CO 2 propane oxygen (air) Propane tank N 2 (g) + 2O 2 (g) 2NO 2 (g) 1.5 mol 50.0 g ? 1. Limiting reagent? 2. Maximum g NO 2 produced? 1.5 mol N 2 = 3 mol O 2 3 mol O 2 = 48 g, hence N 2 is limiting agent. 1.5 mol N 2 = 3 mol NO 2 3 mol NO 2 = 3 x 46.01g = 183.03 g

16. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS REACTION YIELDS REACTION YIELD the amount of product obtained in a chemical reaction. THEORETICAL YIELD the calculated amount of product using the balanced chemical reaction. ACTUAL YIELD the (measured) weight in grams or the corresponding amount in moles (molar yield). PERCENTAGE YIELD the percentage of the theoretical amount of product actually produced in the reaction. % YIELD = ---------------------------- X 100 ACTUAL YIELD THEORETICAL YIELD Usually expressed in grams of product. However, depending on the scale of the reaction it could also be given in mg or kg

17. El Camino College Chemistry 21A Dr. Dragan Marinkovic CHEMICAL REACTIONS 2HgO(s) 2Hg(l) + O 2 (g) 7.22 g HgO used 5.90 g Hg collected % yield = ? HgO f.w. = 216.6 Hg f.w. = 200.6 2 mol HgO gives 2 moles Hg 1 mol HgO gives 1 mol Hg 7.22 g Moles HgO used = ------------- = 0.0333 216.6 g theoretical yield of Hg = 0.0333 x 200.6 g = (6.6867 g) 6.69 g 5.90 g percentage yield = ------------------ x 100 = 88.19% 6.69 g REACTION YIELD