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Types of Reactions6 major types. predict the products predict whether or not they will happen at allHow? We recognize them by their reactants
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#1 - Combination Reactions Combine = put together 2 substances combine to make one
cmpd (also called “synthesis”) Ca + O2 CaO
SO3 + H2O H2SO4
predict products, especially if reactants are 2 elements
Mg + N2 Mg3N2 (symbols, charges, cross)
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Complete and balance: Ca + Cl2 Fe + O2 (assume iron (II) oxide is the product)
Al + O2 Remember first step…write correct
formulas – you can still change subscripts at this point, but not while balancing!
Then balance by changing just coefficients only
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#1 – Combination ReactionsAdditional Notes:
a) Some nonmetal oxides react with H2O - produces acid:
SO2 + H2O H2SO3
b) Some metallic oxides react with H2O - produces base:
CaO + H2O Ca(OH)2(how “acid rain” forms)
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#2 - Decomposition Reactionsdecompose = fall apartone reactant breaks apart into 2 or
more elements or cmpdsNaCl Na + Cl2
CaCO3 CaO + CO2
Note: energy (heat, sunlight, electricity, etc.) usually required
electricity
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#2 - Decomposition Reactionspredict products if binary cmpd
(made of 2 elements)
–It breaks apart into the elements:H2OHgO
electricity
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#3 - Single Replacement ReactionsOne element replaces another (new
dance partner)
Reactants must be an element & cmpd
Products will be a different element and different cmpd
Na + KCl K + NaCl F2 + LiCl LiF + Cl2
(Cations switched)
(Anions switched)
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#3 Single Replacement Reactions Metals replace other metals (they can
also replace H) K + AlN Zn + HCl Think of water as: HOH
–Metals replace first H, then combines w/ hydroxide (OH).
Na + HOH
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#3 Will a single replacement reaction occur?
can even tell whether or not single replacement rxn will happen:–b/c some chemicals more “active” than
others–More active replaces less active
Look at Activity Series of Metals–Higher on list replaces lower
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The “Activity Series” of Metals Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead HydrogenHydrogen Bismuth Copper Mercury Silver Platinum Gold
1) Metals can replace other metals, if they are above metal trying to replace (i.e. Zn will replace Pb)
2) Metals above H can replace H in acids.
3) Metals from Na upward can replace hydrogen in H2O
Higher activity
Lower activity
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The “Activity Series” of Halogens
Fluorine Chlorine Bromine Iodine
Halogens can replace other halogens in compounds, if they are above halogen they are replacing
2NaCl(s) + F2(g) 2NaF(s) + Cl2(g)
MgCl2(s) + Br2(g) ???No Reaction!
???
Higher ActivityHigher Activity
Lower ActivityLower Activity
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#4 - Double Replacement Reactions Two things replace each other.
–Reactants must be two ionic compounds, in aqueous solution
NaOH + FeCl3 –positive ions change place (dance partners)
NaOH + FeCl3 Fe+3 OH- + Na+1 Cl-1
= NaOH + FeCl3 Fe(OH)3 + NaCl
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#4 - Double Replacement Reactions Have certain “driving forces”, or reasons
–only happens if one product:
a) doesn’t dissolve in water & forms a “precipitate”, or
b) is gas that bubbles out, or
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Complete and balance:assume all of the following
reactions actually take place:
CaCl2 + NaOH
CuCl2 + K2S
KOH + Fe(NO3)3
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How to recognize which type?Look at the reactants:
E + E =Combination
C = Decomposition
E + C = Single replacement
C + C = Double replacement
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#5 – Combustion Reactions Combustion means “add oxygen” Normally, a cmpd composed of only
C, H, (and maybe O) is reacted with oxygen – called “burning”
Complete combustion, products are CO2 and H2O
If incomplete, products are CO or C and H2O
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#6 – Acid Base Acid with a base produces a salt and
water The cation in the salt comes from the
base; the anion come from the acid
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Examples of Acid/Base HCl (aq) + Ca(OH)2 (aq) CaCl2 (aq) + H2O (l)
Acid Base Salt Water
H2SO4 (aq) + Fe(OH)3 Fe2(SO4)3 (aq) H2O
Acid Base Salt Water
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SUMMARY: An equation... Describes a rxn Must be balanced (follows the Law of
Conservation of Mass) only balance by changing coefficients special symbols to indicate physical
state, catalyst or energy required, etc.
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