Chapter 7 Chemical Reactions

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Chapter 7Chemical Reactions
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Chemical Reactions

• Chemical reactions are processes in which one set
  of chemicals are converted to a new set of
  chemicals
• Chemical reactions are described by chemical
  equations.

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Evidence for Chemical Reactions

• A gas is produced.
• A precipitate is formed.
• A permanent color change is observed.
• An energy change occurs.

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Chemical Equations

• N2 (g) 3 H2 (g) ? 2 NH3 (g)
• must be balanced to satisfy Law of conservation
  of mass
• State Designations
• (g) gas
• (l) liquid
• (s) solid
• (aq) aqueous

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• Copper(II) oxide reacts with ammonia (NH3) to
  yield copper, nitrogen gas, and water.
• Write a balanced equation for this reaction.

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• Ammonia reacts with oxygen gas to form nitrogen
  monoxide and water.

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• Zinc metal reacts with hydrochloric acid to
  produce zinc chloride and hydrogen gas.
• Potassium chlorate when heated, decomposes to
  form potassium chloride and oxygen gas.

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• Hexane(C6H14) burns in oxygen gas to form carbon
  dioxide and water.
• Lead(II) nitrate reacts with potassium chromate
  to form lead(II) chromate (yellow ppt.) and
  potassium nitrate.

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Some more examples

• N2 H2 ?? NH3
• Be2C H2O ?? Be(OH)2 CH4
• HCl CaCO3 ?? CaCl2 H2O CO2
• C2H6 O2 ?? CO2 H2O

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Electrolyte

• Substances such as NaCl of KBr, which conduct
  electricity when dissolved in water. Dissociates
  to produce ions in solution.

Non electrolyte

• Substances such as sucrose, which do not conduct
  electricity when dissolved in water. Do not
  produce ions in solution.

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Dissociation

• The breaking apart of a molecular substance into
  ions in solution.

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NaCl(aq) AgNO3(aq) ? AgCl(s) NaNO3(aq)
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Writing ionic equations

• Soluble ionic substances are written as ions.
• Strong acids and bases are written as ions.
• HClO4 NaOH
• H2SO4 KOH
• HBr Ba(OH)2
• HCl Ca(OH)2
• HNO3 all soluble hydroxides
• Weak acids and bases are written in the
  undissociated form.
• Weak electrolytes or insoluble salts written as
  molecular formula.

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Solubility Rules

• Alkali metals and NH4 compounds are soluble.
• Nitrates(NO3?), acetates (CH3CO2?), chlorates
  (ClO3?), and perchlorates(ClO4?) are soluble.
• Chlorides(Cl?), bromides(Br?), iodides(I?), are
  soluble except for Silver(Ag),mercury(I)(Hg22),
  and lead(II)( Pb2) halides.
• Sulfates(SO4?2) are soluble except for Sr2,
  Ba2, Pb2, and Hg22.
• Hydroxides(OH?) are insoluble except for alkali
  metals and NH4 (see1).
• Sulfides(S?2), carbonates(CO3?2),
  phosphates(PO4?3), and chromates(CrO4?2) are
  insoluble except for alkali metals and NH4
  (see1).

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• Vinegar(acetic acid) reacts with baking soda
  (sodium bicarbonate) to produce carbon dioxide
  gas, sodium acetate, and water.

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• Iron(III) chloride reacts with ammonium hydroxide
  to form iron(III) hydroxide (brown ppt.) and
  ammonium chloride.
• Barium hydroxide and ammonium chloride react to
  form ammonia (NH3), water, and barium chloride.

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Classifying Reactions by Type of Chemistry
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Classifying Reactions by Type of Chemistry

• Precipitation AX BZ ?? AZ BX
• Acid Base HX BOH ?? BX H2O
• Gas Evolution
• H2X BCO3 ? H2O CO2(g) BX
• H2X BSO3 ? H2O SO2(g) BX
• NH4X BOH ? H2O NH3(g) BX
• Oxidation Reduction A2 B ?? A B2
• Combustion CxHxOxO2?CO2 H2O

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Classifying Reactions by what Atoms Do
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Classifying Reactions by what Atoms Do

• Combination/Synthesis A Z ?? AZ
• Decomposition AZ ?? A Z
• Single Displacement A BZ ?? AZ B
• Double displacement AX BZ ?? AZ BX
• Neutralization HX BOH ?? BX H2O

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Predicting ReactionsDouble Displacement
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BaCl2 ZnSO4 ?

• Conventional equation
• BaCl2(aq) ZnSO4(aq) ? BaSO4(s) ZnCl2(aq)
• Total ionic equation
• Ba2(aq) 2Cl-1(aq) Zn2(aq) SO4-2(aq) ?
  BaSO4(s) Zn2 (aq) 2Cl-1(aq)
• Net ionic equation
• Ba2(aq) SO4-2(aq) ? BaSO4(s)

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AgNO3 Na2SO4?

• AgNO3 Na2SO4? NR

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(NH4)2CO3 CaCl2 ?

• (NH4)2CO3 CaCl2 ? 2 NH4Cl CaCO3(s)

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Na2S ZnCl2 ?

• Na2S ZnCl2 ?2 NaCl ZnS(s)

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K3PO4 Sr(NO3)2 ?

• 2 K3PO4 3 Sr(NO3)2 ? 6 KNO3 Sr3(PO4)2 (s)

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Mg(NO3)2 NaOH ?

• Mg(NO3)2 2 NaOH ? Mg(OH)2(s) 2 NaNO3

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Ba(OH)2 H3PO4 ?

• 3 Ba(OH)2 2 H3PO4 ? Ba3(PO4)2(s) 6 H2O

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HClO4 NaOH ?

• HClO4 NaOH ? H2O(l) NaClO4

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H3PO3 NH3 ?

• H3PO3 3 NH3 ? (NH4)3PO3

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CH3COOH KOH ?

• CH3COOH KOH ? CH3COO-K H2O

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NH4Cl KOH ?

• NH4Cl KOH ? (NH4OH KCl) ?
• NH3 HOH KCl

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K2CO3 HCl ?

• K2CO3 2 HCl ? (H2CO3 2 KCl)
• ?H2O CO2 2 KCl

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K2SO3 HCl ?

• K2SO3 2 HCl ? (H2SO3 2 KCl)
• ?H2O SO2 2 KCl

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H2CO3 Ca(NO3)2 ?

• H2CO3 Ca(NO3)2 ? CaCO3(s) 2 HNO3

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Fe(NO3)3 NH3 ?

• Fe(NO3)3 3NH3 3H2O? Fe(OH)3(s) 3NH4NO3

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More

• K2S CuSO4 ?
• Na2CrO4 Pb(C2H3O2)2 ?
• ZnBr2 K3PO4 ?
• KOH NH4Cl ?
• NH3 HCN ?

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Predicting Reactions Single Displacement (AKA
Single Replacement)
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Pb Zn(NO3)2 ?
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Fe HCl ?
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Cu AgNO3?
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Cr Zn(NO3)2 ?
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Pb Sn(NO3)2 ?
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H2 NiCl2 ?
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Cr NiCl2 ?
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H2 Au(NO3)2 ?