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El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
CHEMICAL EQUATIONS
magnesium + chlorine magnesium chloride
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
CHEMICAL EQUATIONS
Mg(s) + Cl2 (g) MgCl2(s)
magnesium + chlorine magnesium chloride
REACTANTS PRODUCTS
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
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
CHEMICAL REACTIONS
COMBINATIONDOUBLE
REPLACEMENT (METATHESIS)
DECOMPOSITION COMBINATIONSINGLE
REPLACEMENT (SUBSTITUTION)
DECOMPOSITION
NONREDOX REDOX
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
REDOX REACTIONS
OXIDATION REACTIONS(originally) reactions with oxygennowadays:- 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 lostnowadays:- process of gaining electrons(increase of negative charge, i.e./or decrease in positive charge) =an oxydation number decrease
During ANY redox reactionelectrons are exchanged
between atoms and/or ions;some are oxidized others
are reduced.
rusty iron fire
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
REDOX REACTIONS
Na Na+ + e-
Cl + e- Cl-
Na + Cl Na+Cl-
Mg Mg2+ + 2e-
O + 2e- O2-
Mg + O Mg2+O2-
Ca Ca2+ + 2e-
2F + 2e- 2F-
Ca + 2F Ca2+F2-
OXIDIZED
REDUCED
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
REDOX REACTIONS
Na Na+ + e-
Cl + e- Cl-
Na + Cl Na+Cl-
Mg Mg2+ + 2e-
O + 2e- O2-
Mg + O Mg2+O2-
Ca Ca2+ + 2e-
2F + 2e- 2F2-
Ca + 2F Ca2+F2-
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. = 0Ia group: O.N. = +1Iia group: O.N. = +2hydrogen: O.N. = +1oxygen: O.N. = -2O (in peroxides only): O.N. = -1sum of all atomsin a compound O.N. = 0sum of all atoms in polyatomic ion O.N. = ion
charge
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.
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
DECOMPOSITION REACTIONS
2H2O2 2H2O + O2(g)
CaCO3(s) CaO (s) + CO2(g)
DECOMPOSITION REACTION: A single substance reacts to form two or more simpler substances.
Aragonite Calcite
Vaterite or (μ-CaCO3) Chalk
Limestone Marble
Travertine 500 milligram calcium supplements made from calcium carbonate
2HgO(s) 2Hg(l) + O2(g)
Montroydite
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 forma single substance.
S (s) + O2 (g) --> SO2 (g)
2SO2(g) + O2 (g) --> 2SO3 (g)
SO3(g) + H2O (l) --> H2SO4 (aq)
2000 United States chemical industryCHEMICAL 2000 PRODUCTION
PRODUCTIONRANK (in 109 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 REACTIONTwo compounds react and exchange partners to form two new compounds.
AgNO3(aq) + KCl(aq) ‑‑‑‑> AgCl(s) + KNO3(aq)
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(NO3)2 --> 2KNO3 + PbI2(s)
2K+(aq) + 2I-(aq) + Pb2+(aq) + 2NO3-(aq) --> 2K+(aq) + 2NO3
-(aq) + PbI2(s)
2I-(aq) + Pb2+(aq) --> PbI2(s)
2K+(aq), 2NO3-(aq)
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
H+(aq) + Cl−(aq) + Na+(aq) + OH−(aq) → Na+(aq) + Cl−(aq) + H2O(l)
H+(aq) + OH−(aq) → H2O(l)
Cl−(aq), Na+(aq)
NEUTRALIZATION REACTION
NEUTRALIZATION REACTION
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
ENERGY and REACTIONS
H+(aq) + OH−(aq) → H2O(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) + H2O(l) + energy
HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) ∆H = 13.36 kcalmol-1
EXOTHERMIC REACTION (heat release)
ENDOTHERMIC REACTION (heat absorption)
C3H8 + 5O2 ---> 4H2O + 3CO2 + energypropane + oxygen water + carbon dioxide + energy
heat, light
("cold-packs.")
Combustion reaction
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
The MOLE and CHEMICAL EQUILIBRIUM
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)
C3H8(g) + 5O2(g) ---> 4H2O(l) + 3CO2(g)
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)
C3H8(g) + 5O2(g) ---> 4H2O(l) + 3CO2(g)
1 mol C3H8 + 5 mol O2 ---> 4 mol H2O + 3 mol CO2
44 g C3H8 + 160 g O2 ---> 72 g H2O + 132 g CO2
How many moles and grams of water and carbon dioxide will be obtained if 11 g of propane was burned?
11 gMoles of C3H8 = ------------ = 0.25
44 g
Moles of H2O = 4 x 0.25 = 1.00 gH2O = 1.00 x 18.0 = 18 g
Moles of CO2 = 3 x 0.25 = 0.75 gCO2 = 0.75 x 44.0 = 33.0 g
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONSThe LIMITING REACTANT
LIMITING REACTANTThe 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 PRINCIPLEThe 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 EXCESSis the reactant that is not completely used up during the chemical reaction, that is, there is some of this reactant left over.
C3H8 + 5O2 ---> 4H2O + 3CO2 propane oxygen (air)
Propane tank
N2(g) + 2O2(g) 2NO2(g)
1.5 mol 50.0 g ?1. Limiting reagent? 2. Maximum g NO2 produced?
1.5 mol N2 = 3 mol O2
3 mol O2 = 48 g, hence N2 is limiting agent.
1.5 mol N2 = 3 mol NO2
3 mol NO2 = 3 x 46.01g = 183.03 g
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONSREACTION YIELDS
REACTION YIELDthe amount of product obtained in a chemical reaction.
THEORETICAL YIELDthe calculated amount of product usingthe 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 100ACTUAL 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
El Camino College Chemistry 21A Dr. Dragan Marinkovic
CHEMICAL REACTIONS
2HgO(s) 2Hg(l) + O2(g)
7.22 g HgO used 5.90 g Hg collected
% yield = ?
HgO f.w. = 216.6Hg f.w. = 200.6
2 mol HgO gives 2 moles Hg1 mol HgO gives 1 mol Hg
7.22 gMoles 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