equations & balancing. outline word equations skeleton equations conservation of mass ...
TRANSCRIPT
Equations & Equations & BalancingBalancing
OutlineOutline
Word EquationsWord Equations Skeleton EquationsSkeleton Equations Conservation of MassConservation of Mass Balanced Chemical EquationsBalanced Chemical Equations
Chemical EquationsChemical Equations Represent a Represent a chemical reactionchemical reaction..
Are made up of Are made up of twotwo parts: parts:
ReactantsReactants ProductsProducts
eg. methane + oxygen eg. methane + oxygen carbon dioxide + carbon dioxide + waterwater
CHCH44 + O + O22 CO CO22 + H + H22OO
Chemical EquationsChemical Equations
ReactantsReactants are listed on the are listed on the left sideleft side and and separatedseparated by a by a plus sign (+).plus sign (+).
ProductsProducts are listed on the are listed on the right sideright side and and separatedseparated by a by a plus sign (+).plus sign (+).
Word EquationsWord Equations
Word EquationsWord Equations – only the chemical – only the chemical names of the reactants and products names of the reactants and products are shown.are shown.
eg. eg. methane + oxygen methane + oxygen carbon dioxide + carbon dioxide + waterwater
Skeletal EquationsSkeletal Equations
Unbalanced system where the Unbalanced system where the chemical names are converted to chemical names are converted to chemical symbols/formulas.chemical symbols/formulas.
Eg.Eg. CHCH44 + O + O22 CO CO22 + H + H2200
Conservation of MassConservation of Mass
MassMass of the of the reactantsreactants = the = the massmass of of the the productsproducts..
Why?Why? AtomsAtoms are not are not created or destroyedcreated or destroyed
in a chemical change.in a chemical change.
FormulasFormulas for molecules for molecules cannotcannot be be changed.changed.
Balanced Chemical EquationBalanced Chemical Equation
When the When the reactantsreactants and and products products contain contain equal numbersequal numbers of the of the same atom the chemical equation same atom the chemical equation is is balancedbalanced..
Balanced by the use of coefficientsBalanced by the use of coefficients
Balanced Chemical EquationBalanced Chemical Equation
CoefficientsCoefficients are numbers written are numbers written in in frontfront of chemical formulas. of chemical formulas.
They They indicate numberindicate number of atoms or of atoms or molecules of that molecules of that substance.substance.
CHCH44 + + 22OO22 CO CO22 + + 22HH2200
CoefficientCoefficient
Balanced Chemical EquationBalanced Chemical Equation
Physical state symbols are added Physical state symbols are added to show the substance’s to show the substance’s compositioncomposition
((s) – solids) – solid (l) – liquid (l) – liquid (aq) – aqueous(aq) – aqueous (g) - gas(g) - gas
CHCH4(g)4(g) + + 22OO2(g)2(g) CO CO2(g)2(g)+ + 22HH220 0 (l)(l)
Balancing EquationsBalancing Equations
CHCH44 + O + O22 CO CO22 + H+ H2200
Type of atom Type of atom (symbol)(symbol)
# in reactants# in reactants # in products# in products
CC 1 1 1 1
HH 44 22
00 22 33
Balancing EquationsBalancing Equations
CHCH44 + O + O22 CO CO22 ++ 22HH2200
Type of atomType of atom
(symbol)(symbol)# in reactants# in reactants # in products# in products
CC 1 1 1 1
HH 44 44
00 22 44
Balancing EquationsBalancing Equations
CHCH44 + + 22OO22 CO CO22 ++ 22HH2200
Type of atomType of atom
(symbol)(symbol)# in reactants# in reactants # in products# in products
CC 1 1 1 1
HH 44 44
00 44 44
Balanced Chemical EquationBalanced Chemical Equation
General RulesGeneral Rules1)1) Balance metals Balance metals firstfirst..2)2) Balance Balance non-metalsnon-metals next (except next (except
hydrogen and oxygen). Polyatomic hydrogen and oxygen). Polyatomic ions can be balanced as a group.ions can be balanced as a group.
3)3) Balance Balance hydrogenhydrogen and and oxygenoxygen last. last.4)4) Ensure that the eqn is in lowest terms.Ensure that the eqn is in lowest terms.5)5) Check to ensure that there are the Check to ensure that there are the
same # of each type of atom before same # of each type of atom before and after the rxnand after the rxn
Balanced Chemical EquationBalanced Chemical Equation
Use Use coefficients coefficients to change the to change the numbernumber of atoms of an element. of atoms of an element.
NeverNever change the change the subscriptssubscripts..
Some equations may take longer Some equations may take longer than others to solve (than others to solve (be patientbe patient).).