Sunday, February 12, 2012
Energy Diagrams and Calculations--By Tina Zhao
Energy Diagrams:
Important Terms:
Energy of reactants: Total potential energy of all reactants in the reaction
Energy of product: Total potential energy of all products in the reaction
Energy of the activated complex: potential energy of the "transition state" between reactants
and products.
Activation energy: The energy that must be added to get the reaction to progress
Enthalpy: It is the energy of products - energy of reaction
There are some examples
（http://www.sciencegeek.net/Chemistry/taters/energydiagram.htm）
Energy in the Equation
- The energy absorption or release can be placed directly in the equation.
Exothermic : Reactions have the energy term on the right hand side and a negative H
example: CH4 + 2O2 ------CO2 + 2H2O + 812KJ
Endothermic: Reaction have the energy term on the left hand side and a positive H
example: I2 + Br2 + 81.5KJ -------2IBr
Energy Calculations
- The value of H change of a reaction and is expressed in KJ per mole of one of the chemical.
- We ignore the negative in conversion calculation because we use words
example: Using the follow reaction, how many moles of CH4 are needed to produce 2100KJ
of energy?
CH4 + 2O2 ------- CO2 + 2H2O + 812 KJ
2100KJ x 1mole of CH4 / 812KJ = 2.6moles of CH4
Important Terms:
Energy of reactants: Total potential energy of all reactants in the reaction
Energy of product: Total potential energy of all products in the reaction
Energy of the activated complex: potential energy of the "transition state" between reactants
and products.
Activation energy: The energy that must be added to get the reaction to progress
Enthalpy: It is the energy of products - energy of reaction
There are some examples
（http://www.sciencegeek.net/Chemistry/taters/energydiagram.htm）
Energy in the Equation
- The energy absorption or release can be placed directly in the equation.
Exothermic : Reactions have the energy term on the right hand side and a negative H
example: CH4 + 2O2 ------CO2 + 2H2O + 812KJ
Endothermic: Reaction have the energy term on the left hand side and a positive H
example: I2 + Br2 + 81.5KJ -------2IBr
Energy Calculations
- The value of H change of a reaction and is expressed in KJ per mole of one of the chemical.
- We ignore the negative in conversion calculation because we use words
example: Using the follow reaction, how many moles of CH4 are needed to produce 2100KJ
of energy?
CH4 + 2O2 ------- CO2 + 2H2O + 812 KJ
2100KJ x 1mole of CH4 / 812KJ = 2.6moles of CH4
Endothermic/exothermic Reaction -- by Ria Park
All chemical reactions make changes in energy. Those are:
Endothermic Reaction:
- This reaction absorbs energy.
- e.g. one ice pack melts. -> it absorbs energy so that ice becomes water.
- It takes more energy to break bonds.
Exothermic Reaction:
- This reaction release energy.
- 2 explosion explode. -> it release energy.
- It takes takes less energy to break bonds.
> Chemical bonds hold molecules together.
- add energy to break bonds
- lose energy to to join together again.
> Enthalpy(H) is the heat contained in the reactions.
Balancing Equation --By Tina Zhao
Balancing Equation:
- The aim of balancing equation is to make the number of atoms of each kind on the reactant side equal to those on the product side.
Rule:
-Chemical formulas of reactants are listed on the lefthand side of the equation.
-Products are listed on the righthand side of the equation.
-Reactants and products are separated by putting an arrow between them to show the direction of the reaction. Reactions at equilibrium will have arrows facing both directions.
- First balance the atoms which only occur in one molecule on each side of equation
Balance whole group whenever possible, rather than considering the atoms of groups separately
- Be systematic: do not jump all over an equation balancing a bit here and bit these
-balance atoms which occur in elemental from last. By elemental form we mean that the atoms are not combined with atoms of a different kind.
- The aim of balancing equation is to make the number of atoms of each kind on the reactant side equal to those on the product side.
Rule:
-Chemical formulas of reactants are listed on the lefthand side of the equation.
-Products are listed on the righthand side of the equation.
-Reactants and products are separated by putting an arrow between them to show the direction of the reaction. Reactions at equilibrium will have arrows facing both directions.
- First balance the atoms which only occur in one molecule on each side of equation
Balance whole group whenever possible, rather than considering the atoms of groups separately
- Be systematic: do not jump all over an equation balancing a bit here and bit these
-balance atoms which occur in elemental from last. By elemental form we mean that the atoms are not combined with atoms of a different kind.
Example for balancing equation:
http://www.files.chem.vt.edu/RVGS/ACT/notes/scripts/bal_eq1.htm
step 1:
step2:
step3:
step4:
Open these links, these links may help you for balancing equation.
Covalent Compound:
Ionic Compound:
Ionic compounds are basically defined as being compounds where two or more ions are held next to each other by electrical attraction. One of the ions has a positive charge (called a "cation") and the other has a negative charge ("anion").I
|
example:
NaCI : Sodium Chloride
K2SO4：potassium Sulphate
FE2O3: Iron(III）Oxide
-Bonding between non-metals consists of two electrons shared between two atoms.
Mono: 1 Di:2 Tri:3 Tetra:4 Penta: 5 Hexa:6 Hepta:7 Octa:8 Nona:9 Deca:10 Hendeca:11 Dadeca:12
Translating word equations/naming compounds -- by Ria Park
Sometimes we need to translate balancing equations into word equations. There are some rules that they have to follow.
For ionic compounds:
NaCl -> Sodium Chloride
MgCl₃ -> Magnesium Chloride
Fe₂O₃-> Iron(Ⅱ) Oxide
For Covalent Compounds:
mono 1
di 2
tri 3
tetra 4
penta 5
hexa 6 >> Put any of these infront of the names of non-metals
hepta 7
Octa 8
nona 9
deca 10
hendeca 11
dodeca 12
CO₂Carbon dioxide
CO carbon monoxide
Acids:
HCl Hydro chloric acid
H₂SO₄Sulfuric aicd
H₂SO₃Sulfurous acid
HNO₃Nitric acid
E.g.
For ionic compounds:
NaCl -> Sodium Chloride
MgCl₃ -> Magnesium Chloride
Fe₂O₃-> Iron(Ⅱ) Oxide
- Put '-ide' at the and of the names of non-metals
For Covalent Compounds:
mono 1
di 2
tri 3
tetra 4
penta 5
hexa 6 >> Put any of these infront of the names of non-metals
hepta 7
Octa 8
nona 9
deca 10
hendeca 11
dodeca 12
CO₂Carbon dioxide
CO carbon monoxide
Acids:
HCl Hydro chloric acid
H₂SO₄Sulfuric aicd
H₂SO₃Sulfurous acid
HNO₃Nitric acid
- --ate -> --ic
- --ite -> --ous
E.g.
- Cu + 2AgNO₃-> Cu(NO₃)₂+ 2Ag ==>> Copper + silver nitrate -> copper nitrate + silver
- Cu + I -> CuI ==>> Copper + Iodine -> Copper Iodide
- C₃H8 + O₂ -> CO₂+ H₂O ==>> Trioxide Octahydride -> Carbon dioxide + water
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