chemical reactions an expression of the behavior of chemical compounds 1. expressed in a chemical...
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Chemical ReactionsAn expression of the behavior of
chemical compounds
1. Expressed in a chemical equation:
Reactant(s) Product(s)(compounds reacting) To Yield (reconstituted
compounds)
Parts of a Chemical Equation
2 Na(s) + 2H2O(l) 2NaOH (aq) + H2(g)
To Yield
Subscripts: # of atoms in compound
Physical State: (s), (l), (g), (aq)
Coefficient: the # of cpd (moles) present. Can be factions, ONLY # that is changed
Reversible reaction: Catalyst: heat, Δ, or compound (FeO2)
Balancing Chemical Equations
ONLY the coefficient can be changed.1. write the compounds (criss-cross) or prefix for molecules.2. Define the type of reaction (activity series and solubility rules)3. Take count of the type and number of elements in the compounds.4. Change of the coefficient ONLY to ensure that the same # and type of each are present on both sides of the arrow.
Word Problem
An aqueous solution of sodium chloride and hydrogen sulfide gas is produced when aqueous sodium sulfide reacts with an excess of hydrochloric acid.
Na2S(aq) + HCl(aq) NaCl(aq) + H2S(g)
Word Problem Sampler
Solid lead is dissolved in aqueous sulfuric acid to precipitate lead (III) sulfate and hydrogen gas is evolved.
Pb(s) + H2SO4(aq) Pb2(SO4)3(s) + H 2(g)
Type of Reactions
1. Synthesis Reaction
2. Decomposition Reaction
3. Single Replacement
4. Double Replacement
5. Combustion Reaction.
Synthesis Reaction
The reaction of two or more reaction to produce a single produce.
a. Form:
A2 + 2CB 2ACB
Sulfur dioxide and water react to produce sulfurous acid
SO2 + H2O H2SO3
Decomposition Reaction
A reaction where one or more reactants breakdown into several simpler forms.
a. Form:
AB2 A + 2B
b. Requires energy to breakdown!
Ammonia breaks down to nitrogen gas and hydrogen gas
2NH3 N2 + 3H2
Single Replacement
• A reaction where the metals (or non-metal) trade places.
• a. Form: AB + C CB + A
• b. Depends directly of the activity of the metal.
Activity Series
• Back of periodic table:
• **The more active the metal (or non-metal), the more likely it is to replace the less active metal (or non-metal).
• **All metals will replace Gold according to the list.
• **Lithium will replace all metals.
• **Fluorine is the most active non-metal.
Sample: Single Replacement
• Sodium plus copper (II) chloride yields sodium chloride and copper metal.
2Na + CuCl2
• Magnesium metal reacts with potassium hydroxide to yield
Mg + KOH
Double Replacement
• a reaction where the metals or non-metals trade positions. (like replaces like).
Form:
AB + CD AD + CB
A precipitate can be formed as one of the produces often.
Sample: Double Replacement
Silver (I) nitrate plus sodium chloride to yield sodium nitrate and silver (I) chloride.
**Balance the charge then balance the equation**
AgNO3 + NaCl
AgNO3 + NaCl NaNO3 + AgCl
Solubility
Ionic compounds ability to dissolve in water.
Solubility Rule:
Note the Periodic Reference Page
Ba(NO3)2
Pb2(SO4)3
C2H4
AgCl2CaCO3
Combustion Reaction
The burning of hydrocarbons in the presents of oxygen and energy.
– Form: Hydrocarbon gas + oxygen carbon dioxide and water. (a complete burn).
CH4 + O2 CO2 + H2O
(a complete burn)
Or
CH4 + O2 CO + H2O
(a dirty burn)
Net Ionic EquationsSpectator Ions: Occurs when reactant
compounds dissolve into solution and ions remain in solution.
– Pay attention to the physical state. (s) indicates that it has NOT ionized (broken down)
– Pay attention to the solubility rules on the periodic table.
– The ions that are on both sides of the equation are called spectator ions and cancel.
– The ions that remain form a net ionic equation.
Sample: Net Ionic Equation
Pb(ClO4)2 (aq) + NaI(aq) PbI2(s) + NaClO4(aq)
Chemical Equation
2Na (s) + 2H2O (l) 2NaOH (aq) + H2(g)
reactants To Yield Products
(s) : solids (l) : liquid (aq): aqueous (g): gas
Coefficient: Big number in front. # of compounds present (# of moles). ONLY number that can change.
Subscript: # of atoms present in the compound
Reversible; Catalyst
Chemical Reaction
An expression of the behavior of chemical compounds
Expressed in a chemical equation:
To yield
Reactant(s) Product(s)
(stuff reacting) (reforming of stuff)
****Energy is required to break or form****
Balancing Chemical EquationsSame number and type of each element
on both sides of the . *Same by changing the coefficient ONLY.*Coefficient in front of cpd ONLY.*Once the charges of a cpd are balanced, NEVER change a subscript!
Review:Writing formula units and molecular formulaCriss-cross to balance charge