Do Now

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Do Now
C2H6O

• What Are These Symbols Called and What
  Information Can Be Derived From Them?

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Aim What are Chemical Formulas and equations?

• Chemical formulas provide information about the
  atomic composition of a substance, and an
  equation allows us to describe a chemical process
  using the names or formulas.

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Chemical Formulas

• Important part of the language of chemistry
  because it tells us something about the
  composition of an element or a compound.
• A formula can be as simple as He (helium) or as
  complex as C6H12O6, (glucose)

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Molecular Compound

• Tells us how many atoms of each element are
  present in one molecule of a compound.
• A compound containing exactly two elements is
  known as a binary compound

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Ionic Compounds
NaCl

• Formed when ions combine
• The formula of an ionic compound has a different
  meaning from the formula of a molecular compound
  because ions do not form separate molecules.

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Why do positive and negative ions combine?

• Ionic compounds are formed because positive and
  negative attract.
• Molecular substances do not contain ions, but the
  atoms behave as if they have charges.
• The numerical value based on the charge of an
  atom is called Oxidation Numbers or Oxidation
  States.
• This number can be positive, negative, or zero.

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Rules for assigning Oxidation Numbers
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Try these problems.

• Find the oxidation number of sulfur in the
  following compounds-
• SO4 2-, S2O3 2-, H2S2O7, S4O6 2-, SO3 2-
• 2. Find the oxidation number of the metal in the
  following complexes-
• AlF6 3-, KClO2, KHSO4, CrF6 3-, AlCl3

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Writing Formulas For Binary Compounds

• Place the atom or ion with positive oxidation
  numbers before those with negative oxidation
  numbers.
• The sum of the oxidation numbers must be zero.

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Naming Binary Compounds

• Naming is done by using the names of the two
  elements that make up the compound

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Naming Binary Compounds

• The element that has a positive oxidation number
  is placed first the element with the negative
  oxidation number is second and the suffix ide
  
  
  is added at the end of the name

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Elements with negative oxidation numbers and
their names in binary compounds

• H- - hydride C4- - Carbide
• N3- - Nitride O2- - Oxide
• F- - Fluoride P3- - Phosphide
• S2- -Sulfide Cl- - Chloride
• Br - - Bromide I - - Iodide

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Stock System

• Many elements have more than one positive
  oxidation number and can form more than one
  binary compound with the same element.
• Fe2 and Fe3 can form two iron oxides
• FeO- Iron(II)oxide
• Fe2O3 Iron (III)oxide

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Try some problems

• Write the formula for each of the following
  compounds
• copper (II) sulfide
• Iron (III) bromide
• Tin (IV) oxide
• Aluminum nitride

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Try some problems

• Name each of the following compounds
• MgF2
• KH
• NiI2
• N2O

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More on naming compounds

• Another system attaches the suffixes ous and
  ic to elements in order to distinguish two of
  their positive oxidation number
• The suffix ous is used with the elements
  smaller oxidation number, and ic with the larger
  number

FeCl2--- ferrous chloride FeCl3----ferric
chloride Cu2O----cuprous oxide CuO-----cupric
oxide Hg2Br2----mercurous bromide HgBr2
-----mercuric bromide
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Polyatomic Ions

• A group of at least two atoms with electrical
  charges
• The group behave as a single unit with fixed
  oxidation number

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Examples of polyatomic ions

• CaSO4
• Fe(NO3)3
• Na3PO4
• (NH4)2CO3

• Calcium Sulfate
• iron (III) nitrate
• sodium phosphate
• ammonium carbonate

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Problems- Naming polyatomic ions

• Name each of the following compounds.
• CuSO4
• AlPO4
• NaHCO3
• Write the formula for each of the following
• Potassium nitrate
• Lead (II) carbonate
• Ammonium acetate

• Answers
• Copper (II) sulfate
• Aluminum phosphate
• Sodium hydrogen carbonate
• KNO3
• PbCO3
• NH4C2H3O2

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Chemical Equations

• Provides a recipe for carrying out a chemical
  reaction
• Write the following as a word problem
• Methane (CH4) gas reacts with oxygen (O2) gas
  to produce carbon dioxide (CO2) gas, liquid water
  (H2O), and heat.
• Replace the names with formulas

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Chemical Equations
PRODUCTS
REACTANTS
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Problem- writing chemical equations

• Write word and formula equations for the
  following process.
• Solid zinc reacts with a water solution of
  hydrogen sulfate to produce hydrogen gas, a water
  solution of zinc sulfate, and heat

• Answer
• Zinc(s) hydrogen sulfate (aq) hydrogen(g)
  zinc sulfate (aq) heat
• Zn(s) H2SO4 (aq) H2 (g)
  ZnSO4 (aq) heat

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Balancing A Chemical Equation

• All chemical reactions must obey three
  conservation Laws conservation of matter
  (mass), conservation of energy, and conservation
  of electric charge.
• The total mass, energy content, and electric
  charge of the reactants must equal those of the
  products.

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Balancing A Chemical Equation

• According to the Law of conservation of matter,
  what is wrong with this equation?
• CH4(g) O2 (g) CO2 (g) H2O
  (aq) heat
• Balanced Equation
• CH4 (g) 2O2 (g) CO2 (g) 2H2O (l)

• Go to www.studyworksonline.com/
  cda/content/explorat... To get practice in
  balancing equation.

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What are the different forms of chemical
reactions?

• Direct Combination (Synthesis) Reactions
• Decomposition Reactions
• Single-Replacement Reactions
• Double-Replacement Reactions

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Direct Combination (Synthesis) Reactions

• Involves the combination of two or more reactants
  to produce one product.
• The reactants can be elements or compounds.
• They take the form X Y XY

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Examples of Synthesis Reactions

• The production of iron (II) chloride from iron
  and chlorine
• Fe (s) Cl2 (g) FeCl2 (s)
• The production of carbon dioxide from the
  combination of carbon and oxygen.
• 2CO (g) O2 (g) 2CO2 (g)

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Try This Problem

• Write the balance equation for the direct
  combination of sodium (s) and bromine (l) to
  produce a solid product.
• Answer
• 2Na (s) Br2 (l) 2NaBr (s)

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Decomposition Reactions

• Involves the breakdown of a single reaction into
  two or more products.
• The opposite of a direct combination reaction.
• Takes the form AB A B

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Example of Decomposition Reactions

• Hydrogen peroxide decomposes into water and
  oxygen.
• 2H2O2 (l) 2H2O (l) O2 (g)

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Try This Problem

• Write a balance equation for the decomposition of
  ammonia gas (NH3) into its elements
• Answer
• 2NH3 (g) N2(g) 3H2(g)

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Single- Replacement Reactions

• An uncombined element replaces another element
  that is part of a compound
• As a result, the replaced element becomes
  uncombined.
• E FG EG F

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Example of Single- Replacement Reactions

• Element zinc replaces the element copper from a
  aqueous solution of the compound copper (II)
  sulfate
• Zn (s) CuSO4 (aq) ZnSO4 (aq) Cu (s)

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Try This Problem

• Write a balance equation in which the uncombined
  element bromine replaces iodine from a aqueous
  solution of potassium iodide. uncombined
  bromine(Br2) is a liquid, and uncombined iodine
  (I2) is a solid.
• Answer
• Br2 (l) 2KI (aq) 2KBr(aq) I2 (s)

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Double-Replacement Reaction

• Two elements in different compounds replace each
  other.
• Takes the form
• PQ RS PS RQ

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Example of Double-Replacement Reaction

• Aqueous solutions of barium nitrate and sodium
  sulfate are mixed, barium and sodium replace each
  other.
• Ba(NO3)2 (aq) Na2SO4 (aq) BaSO4 (s)
  2NaNO3(aq)