Chemical Reactions reactants products Balancing chemical equations Types of chemical reactions.

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Chemical Reactions reactants products Balancing chemical equations Types of chemical reactions

Transcript of Chemical Reactions reactants products Balancing chemical equations Types of chemical reactions.

Page 1: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

Chemical Reactionsreactants products

Balancing chemical equationsTypes of chemical reactions

Page 2: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

How reactants are transformed into products?

• Reactants are transformed during chemical reactions

• Energy is required (absorbed) to break a chemical bond

• Energy is released when a chemical bond forms

Page 3: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

Balancing equations

• Obey law of conservation of matter• Chemical equations have two

parts: reactants and products

Page 4: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

How to balance?

• The total number of atoms of each element should be the same on both sides of equation

• Use coefficients to balance equations

Example:

2H2 + O2 2 H2O

Page 5: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

Types of chemical reactions

• Single replacement• Double replacement• Decomposition• Combination • Combustion

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Synthesis (Combination) Synthesis (Combination) ReactionsReactions

Two or more substances combine to form a new compound.

A + X AX

Reaction of elements with oxygen and sulfur Reactions of metals with Halogens Synthesis Reactions with Oxides There are others not covered here!

Page 7: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

Decomposition Decomposition ReactionsReactions

A single compound undergoes a reaction that produces two or more simpler substances

Decomposition of:   Binary compounds 2H2O(l ) 2H2(g) +

O2(g)   Metal carbonates CaCO3(s) CaO(s) +

CO2(g)   Metal hydroxides Ca(OH)2(s) CaO(s) +

H2O(g)   Metal chlorates 2KClO3(s) 2KCl(s) +

3O2(g)   Oxyacids H2CO3(aq) CO2(g) +

H2O(l )

AX A + X

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Decomposition ReactionsSulfatesWith the exception of alkali metals and alkaline sulfates, all other metals are decomposed by heat to form a metal oxideNitrates Alkali metals decompose on heating to yield the nitrites and oxygen. All other metal nitrates are decomposed to nitrogen dioxide, oxygen, and the metal oxide on heating.

Page 9: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

Single Replacement Single Replacement ReactionsReactions

Replacement of:

Metals by another metal Hydrogen in water by a metal Hydrogen in an acid by a metal Halogens by more active halogens

A + BX AX + B

BX + Y BY + X

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The Activity Series of the The Activity Series of the MetalsMetals

  Lithium   Potassium   Calcium   Sodium   Magnesium   Aluminum   Zinc   Chromium   Iron   Nickel   Lead   Hydrogen Hydrogen   Bismuth   Copper   Mercury   Silver   Platinum   Gold

Metals can replace other metals provided that they are above the metal that they are trying to replace.

Metals above hydrogen can replace hydrogen in acids.

Metals from sodium upward can replace hydrogen in water

Page 11: Chemical Reactions reactants  products Balancing chemical equations Types of chemical reactions.

Mg + AlCl3

Al + MgCl2

Predict if these reactions will occurAl + MgCl2

Can magnesium replace aluminum?

Activity Series

YES, magnesium is more reactive than aluminum.

2 23 3

Can aluminum replace magnesium?

Activity Series

NO, aluminum is less reactive than magnesium.

Therefore, no reaction will occur.

No reaction

MgCl2 + Al No reaction

The question we must ask is can the single element replace its counterpart? metal replaces metal or nonmetal replaces nonmetal.

Order of reactants DOES NOT

determine how they react.

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The Activity Series of the The Activity Series of the HalogensHalogens

  Fluorine   Chlorine   Bromine   Iodine

Halogens can replace other halogens in compounds, provided that they are above the halogen that they are trying to replace.

2NaCl(s) + F2(g) 2NaF(s) + Cl2(g)

MgCl2(s) + Br2(g) ???No Reaction

???

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Single Replacement Reactions• Sodium chloride solid reacts with fluorine gas

NaCl(s) + F2(g) NaF(s) + Cl2(g)

Note that fluorine replaces chlorine in the compound

• Aluminum metal reacts with aqueous copper (II) nitrate

Al(s)+ Cu(NO3)2(aq) Cu(s) + Al(NO3)3(aq)

2 2

2 3 3 2

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Double Replacement ReactionsDouble Replacement Reactions

The ions of two compounds exchange places in an aqueous solution to form two new compounds.

AX + BY AY + BX

One of the compounds formed is usually a precipitate, an insoluble gas that bubbles out of solution, or a molecular compound, usually water.

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Double Replacement Reactions

• Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together

• Example:

AgNO3(aq) + NaCl(s) AgCl(s) + NaNO3(aq)

• Another example:

K2SO4(aq) + Ba(NO3)2(aq) KNO3(aq) + BaSO4(s) 2

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Combustion ReactionsCombustion ReactionsA substance combines with oxygen, releasing a large amount of energy in the form of light and heat.

  Reactive elements combine with oxygen

P4(s) + 5O2(g) P4O10(s)

(This is also a synthesis reaction)

  The burning of natural gas, wood, gasoline

C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)

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Solubility and precipitation reactions

Pb(NO3)2 (aq) + 2NaI(aq) PbI2(s) + 2NaNO3(aq)

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FeCO3

Na1+Fe2+

iron (II) chloride + sodium carbonate

Cl2

Using a SOLUBILITY TABLE:sodium chloride is soluble

iron (II) carbonate is insoluble

CO3

Fe2+

Fe

Na1+

Na2

Cl1- CO32- Cl1- CO3

2-

NaCl

sodium chloride iron (II) carbonate+

(aq) (ppt)

2FeCl2 Na2CO3 NaCl FeCO3(aq) (ppt)+ +

Predict if a reaction will occur when you combine aqueous solutions of iron (II) chloride with aqueous sodium carbonate solution.

If the reaction does occur, write a balanced chemical equation showing it.

(be sure to include phase notation)

(aq) (aq)

Balanced chemical equation

Complete Ionic EquationFe2+(aq) + 2Cl1-(aq) + 2Na1+(aq) + CO3

2-(aq) 2Na1+(aq) + 2Cl1-(aq) + FeCO3(s)

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Solubility rules

Soluble in water: • sodium, potassium, and ammonium

salts; acetates and nitrates• Halides with the exception of halides

of lead (II), silver(I), and mercury(I).• Sulfates with the exception of

sulfates of calcium, barium, lead (II) and strontium

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Insoluble in water

• Phosphates, carbonates and sulfides except sodium, potassium, ammonium salts, and calcium sulfide

• Hydroxides except sodium, potassium, calcium, and barium hydroxides

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Acid-Base reactions(neutralization reactions)

• Acid: any compound that produces hydrogen ions (H+), when added to water.

• Base: any substance that produces hydroxide ions (OH-), when added to water.

HCl(aq) + Na(OH)(aq) NaCl(aq) + H2O(l)