Chemical Reactions

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Chemical Reactions Equations
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Chemical rxn
Chemical Reactions
Chemical rxns occur when atoms are
Separated
joined
or rear
ranged
As reactants turn into products, what happens to
bon holding atoms together ?
ds
Old Bon are broken new Bon
are formed
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Atoms of 1 element never change into other
elements in chemical rxns (only Nuclear rxns).
Why?
Atoms - neither created nor destroyed just
rearranged in chemical rxns.
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Reactants, products
?
Reactants
Products
_____________
_____________
Left side is called?
Rt. side is called?
What symbol separates the reactants from the
products?
Arrow, which means
Yields, Reacts to produce, To produce
Reactant 1 Reactant 2 ? Product 1 Product 2
and is used to separate 2 products
Reacts with to separate 2 reactants
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Writing chemical eq
II. Writing Chemical Equations
A. Chemical equation
describes reactants products
Chemical equations - described 2ways
Written Words
Skeletal Equation
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rules
Rules for writing chemical eq.
1. Include physical states
Solid (s), Liquid ( l ), Gas (g), Aqueous (aq)
Aqueous means dissolved in water
2. Some elements ONLY appear as diatomics
H2 O2 F2
Br2 I2 N2 Cl2
3. Some rxns require a catalyst.
Catalyst speeds up rxn - not part of product
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rules
4. the catalyst - written above or below ?.
KI
5. If heat is a catalyst, use a
above
What happens if both heat a chemical are
catalysts?
MoS2
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Written words, ex 1
A. Written Words
Ex 1 Fe (s) O2 (g) ? Fe2O3 (s),
interpret
Solid iron
reacts with
oxygen gas
to produce
solid
iron (III) oxide.
Why is oxygen in the example written as O2?
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Written words, ex 2
Written Words
Example 2 KOH (aq) H2SO4 (aq) ? H2O (l)
K2SO4 (aq)
Aqueous potassium hydroxide
reacts with
to yield
water
aqueous sulfuric acid
and
aqueous potassium sulfate.
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skel eq, ex written as symbols
C. Skeletal Equation
What is a skeletal equation?
Ex 1 Manganese (IV) oxide catalyzes the
decomposition of aqueous hydrogen peroxide into
water vapor and oxygen gas.
MnO2
H2O (g)
H2O2 (aq)

O2(g)
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skel eq, ex written as symbols
Skeletal Equation
Ex 2 Solid sodium reacts with water to produce
aqueous sodium hydroxide and hydrogen gas.
H2(g)
Na (s)
?
NaOH (aq)

H2O(l)

Why is hydrogen gas written as H2?
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skel eq, ex written as symbols
Skeletal Equation
Ex 3 Solid sodium hydrogen carbonate reacts
with a solution of hydrochloric acid to produce
aqueous sodium chloride, water and carbon dioxide
gas.
NaHCO3(s)
?
NaCl (aq)

HCl(aq)

H2O (l)

CO2(g)