Accelerated Chemistrychapter 8 Note Packetmr. Seidel

Accelerated Chemistrychapter 8 Note Packetmr. Seidel

Accelerated ChemistryChapter 8 Note PacketMr. Seidel

(student edition)

Chapter 8 problems: # 8, 10, 11, 14, 15, 25, 26, 27, 35, 37, 49

good figures in the book to look at.... Hey, it’s January. Word on the street is that looking at illustrations, tables, and figures in the book is a good idea. I’ve done my best to convince you of that fact.

8.1Chemical Equations

Chemical equations represent, with symbols and formulas, the reactants and products ina chemical reaction.

reactantsproducts

chemical equations describe chemical reactions

requirements for all chemical equations:

  1. must show all reactants and products
  2. formulas must be correct
  3. Law of Conservation of Mass must be satisfied (equation must be balanced)

H2+ Cl22 HCl

sayyields

other example – decomposition of sodium chloride – start from scratch – use symbols, heat, etc.

ex: NaCl (s) = solid sodium chloride NaCl (aq) = solution of sodium chloride (in water)

H2O (l) - liquid water (not aqueous - redundant)

other symbols to know: = one way reactions = reversible reactiongas

= heat = catalyst* = precipitate (solid - only found on products side)

  • a substance that speeds up a reaction without being used up in the reaction

Significance of a chemical equation: H2+ Cl22 HCl means…

Atoms

Molecules

Molar mass

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Balancing Chemical Equations - truly a trial and error process if there ever was one

Helpful hints:

1. 1 atom at a time

2. Balance atoms that appear only 1X per side first

3. Balance polyatomic ions as whole units

4. Balance diatomic elements last

5. Save H + O for last

if this doesn’t succeed, try doubling everything (particularly with combustion)

Let’s try examples from worksheet 8-1…

8.2Types of Chemical Reactions

5 types - synthesis, decomposition, combustion, single replacement, double replacement

remember - first you’ve got to find the right products, then you gotta balance

synthesis ( ) - needs energy to happen

general formula

ex.Ba+SMg+Cl2

Al+Cl2Na+O2

decomposition ( ) - needs energy to happen (usually or )

general formula

ex.FeCl3HgO

MgSO4. 7 H2O 

(hydrate)

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combustion - the reaction of hydrocarbons and oxygen to yield...when you just say cho...

general formula

ex.combustion of CH4, C3H8, C4H10, C2H5OH

single replacement - take place in solution - need very little energy to happen

2 types:

a) General Formula -

exHI+Mg

AlCl3+Ca

Ca+HOH

b) General Formula

exNaCl+ F2

BaS+O2

double replacement - again - aqueous solution - little energy - usually forms one soluble ionic product (aka - aqueous) and either a ppt, water, or a gas that bubbles out of water

general formula

ex.FeCl3+NaOH

H2SO4+NaOH

Page 3NH4Cl+NaOH

8.3Activity Series of the Elements

hey, some reactions happen and some don’t

for synthesis, combustion, and decomposition, we will assume they all happen given sufficient activation energy ( )

for single replacement, use the

Ca + H2OyieldsAl+H2Oyields

Al+HIyieldsCu+HIyields

NaCl +F2NaF+Cl2→

for the activity series, any single element above an element in a compound will replace it

top 5 elements react with

metals above H react with

the nonmetal reactivity series is

for double replacement reactions, use a

1.if one of the products formed is water, the reaction happens

2.if a gas is formed, the reaction happens

3.if an insoluble product forms (I or Ss), the reaction happens (actually a reaction may happen when two soluble products form, but it doesn’t go to completion and is not directly observable)

**** refer to chapter 7 lab, “ions in solution”

examples from the lab - page 1, page 3

Na2CrO4+KCl

FeCl3+KOH

HCl+NaOH

NIB Solubility Trends

Cations -very soluble -

very insoluble-

Anions - very soluble -

for monotomics

very insoluble

sulfides -

general trend -

Showing Energy Changes in Equations

endothermic - put in heat- write on the ______side of the equation

or….

exothermic - releases heat- write on the left side of the equation

Some helpful notes on writing phases in chemical reactions

1. Metals are solids (except )

2. In single and double replacement reactions, reactants that are compounds are always aqueous.

3. In single and double replacement reactions, products that are compounds should have their phases identified using a solubility chart (aqueous vs. precipitate)

4. In synthesis and decomposition reactions, ionic compounds are solids.

5. In combustion reactions, the water, CO2, and O2 are gases. The hydrocarbon is hard to tell, but is usually a liquid after C=6 or higher.

6. Most other covalent compounds are gases.

7. Acids (chemicals starting with hydrogen) are always aqueous.

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