Writing and balancing equations
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Writing And Balancing Equations. Chemistry Dr. May. The Road To Writing Sentences. Know the alphabet Know vowels and consonants Know how to spell words Know the meaning of words Know sentence structure Know capitalization and punctuation. The Road To Writing Equations.

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Writing And Balancing Equations

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Writing and balancing equations

Writing And Balancing Equations

Chemistry

Dr. May


The road to writing sentences

The Road To Writing Sentences

  • Know the alphabet

  • Know vowels and consonants

  • Know how to spell words

  • Know the meaning of words

  • Know sentence structure

  • Know capitalization and punctuation


The road to writing equations

The Road To Writing Equations

  • Know the atomic symbols

  • Know oxidation numbers of elements

  • Know the charge on polyatomic ions

  • Be able to create the correct formulas

  • Identify the reactants and products

  • Balance the equation


The language of equations

The Language of Equations

Ca(OH)2 + H2SO4  CaSO4 + 2 H2O

  • The equation above is like a sentence

  • The compounds Ca(OH)2, H2SO4, CaSO4, and H2O are like correctly spelled and chosen words

  • The elements Ca, O, H, and S are like the letters of the alphabet


Equations in english

Equations in English

Ca(OH)2 + H2SO4  CaSO4 + 2 H2O

  • One molecule of calcium hydroxide plus one molecule of sulfuric acid yields one molecule of calcium sulfate plus two molecules of water.


Equations

Equations

Zn + 2 HCl   ZnCl2 + H2

  • On the left, Zn and HCl are reactants

  • On the right, ZnCl2 and H2 are products

  • The arrow () means “yields”

  • The up arrow () indicated a gas product

  • The 2 in front of HCl is a coefficient

  • The small 2 to the right of H is a subscript


Skeleton equation

“Skeleton” Equation

  • Identify the reaction

    • Zinc reacts with hydrochloric acid to give zinc chloride and hydrogen gas

  • Determine the correct formulas and write the “skeleton” (unbalanced) equation

    • Zn + HCl   ZnCl2 + H2 


Coefficients

Coefficients

  • A coefficient placed before a formula multiplies every atom in that formula by that number

    2 H2SO4

  • 2 H2SO4means 2 molecules ofsulfuric acid but also

  • 4 H atoms, 2 S atoms, and 8 O atoms


Conservation of mass

Conservation Of Mass

  • A balanced equation contains the same number of each kind of atom on each side of the equation

  • The balanced equation obeys the

    Law of Conservation of Mass


Balance the equation

Balance The Equation

Zn + HCl   ZnCl2 + H2 

  • Count atoms of each element on each side

  • Balance each element by placing whole numbers (coefficients) in front of each formula as needed

    Zn + HCl   ZnCl2 + H2

2


Write equation

Write Equation

  • Calcium hydroxide reacts with sulfuric acid to give calcium sulfate and water

Calcium = Ca+2

Hydroxide = OH1

Hydrogen = H+1

Sulfate = SO42

Ca(OH)2 + H2SO4 

CaSO4 + H2O


Balance equation

Balance Equation

Ca(OH)2 + H2SO4  CaSO4 + HOH

Count atoms on both sides

1Ca, 2OH, 2H, 1SO4

1Ca, 1OH, 1H, 1SO4

Balance the water

Ca(OH)2 + H2SO4  CaSO4 + HOH

2


Write equation1

Write Equation

  • Aluminum hydroxide plus sulfuric acid gives aluminum sulfate plus water

Aluminum = Al+3Hydroxide = OH1

Hydrogen = H+1 Sulfate = SO42

Al(OH)3 + H2SO4 

Al2(SO4)3 + H2O


Balance the equation1

Balance The Equation

Al(OH)3 + H2SO4 

Al2(SO4)3 + HOH

1 Al, 3 OH, 2 H, 1 SO4

2 Al, 3 SO4, 1 H, 1 OH

2 Al(OH)3 + H2SO4 

Al2(SO4)3 + HOH

2 Al(OH)3 + 3 H2SO4 

Al2(SO4)3 + HOH

2 Al(OH)3 + 2 H2SO4 

Al2(SO4)3 + 6 HOH


Write the equation

Write The Equation

  • Propane burns to produce carbon dioxide and water

    C3H8 + O2 CO2 + H2O

    The above skeleton equation must be balanced


Balance the equation2

Balance The Equation

C3H8 + O2 CO2 + H2O

  • First balance the carbons

    C3H8 + O2 3CO2 + H2O

  • Next balance the hydrogens

    C3H8 + O2 3 CO2 + 4H2O

  • Finally balance the oxygens

    C3H8 + 5 O2 3 CO2 + 4 H2O

6 + 4 = 10

2 x 5 = 10


Chemical equations

Chemical Equations

  • Chemical equations are the short hand description of a chemical reaction

  • It tells us:

    • The reactants and products

    • The formulas of the reactants and products

    • The number of molecules of reactants and products

    • The number of atoms of each element

    • The number of moles of each substance


The end

The End

  • This presentation was created for the benefit of our students by the Science Department at Howard High School of Technology

  • Please send suggestions and comments to [email protected]


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