el camino college chemistry 21a dr. dragan marinkovic chemical reactions chemical equations...

El Camino College Chemistry 21A Dr. Dragan Marinkovic

CHEMICAL REACTIONS

CHEMICAL EQUATIONS

magnesium + chlorine magnesium chloride


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


CHEMICAL REACTIONS

CHEMICAL REACTIONS

COMBINATIONDOUBLE

REPLACEMENT (METATHESIS)

DECOMPOSITION COMBINATIONSINGLE

REPLACEMENT (SUBSTITUTION)

DECOMPOSITION

NONREDOX REDOX


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


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


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


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.


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


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)


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



CHEMICAL REACTIONS

ENERGY and REACTIONS

H+(aq) + OH−(aq) → H2O(l) ∆H = 13.36 kcalmol-1


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


CHEMICAL REACTIONS

The MOLE and CHEMICAL EQUILIBRIUM


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)


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


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


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


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

el camino college chemistry 21a dr. dragan marinkovic chemical reactions chemical equations...

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