General Chemical Reactions
Any chemical reaction can be described as a Any chemical reaction can be described as a molecular or atomic change. It produces one or molecular or atomic change. It produces one or more observable changes.more observable changes.
e.g. color change, gas bubbles, heat, etc.e.g. color change, gas bubbles, heat, etc. Reactions are generally described as Reactions are generally described as
Reactant(s) Product(s)Reactant(s) Product(s) The reaction is written as a chemical equation The reaction is written as a chemical equation
with chemical formulas:with chemical formulas:
2 Na + Cl2 Na + Cl22 2 NaCl 2 NaCl
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Chemical Equations
Chemical equations describe the change(s) in Chemical equations describe the change(s) in Reactant(s) to Product(s) including physical Reactant(s) to Product(s) including physical state(s).state(s).
Notations: Notations: (g), (l), (s), (aq)(g), (l), (s), (aq) 2 Na 2 Na (s)(s) + Cl + Cl22(g)(g) 2 NaCl 2 NaCl (s)(s) Others: Others:
arrows for gas ( ) and solid ( )arrows for gas ( ) and solid ( )
for heat, for reversibility (equilibrium)for heat, for reversibility (equilibrium)
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Types of Chemical Reactions
Combination (Synthesis)Combination (Synthesis) DecompositionDecomposition Single DisplacementSingle Displacement Double DisplacementDouble Displacement CombustionCombustion Others: Precipitation, Oxidation-Others: Precipitation, Oxidation-
Reduction, NeutralizationReduction, Neutralization
Chemical Reactions
Combination (Synthesis)Combination (Synthesis) A + B CA + B C Example:Example:
• HH2 (g) 2 (g) + O + O2 (g) 2 (g) H H22O O (g) (g)
Balancing (Conservation of Atoms):2 H2 (g) + O2 (g) 2 H2O (g)
Chemical Reactions DecompositionDecomposition A B + CA B + C 2 NI2 NI3 (s)3 (s) N N2 (g)2 (g) + 3 I + 3 I2 (s)2 (s)
Decomposition
Another example:Another example:• Potassium chlorate (s) + heat Potassium chlorate (s) + heat
potassium chloride (s) + oxygen (g)potassium chloride (s) + oxygen (g)• Balanced equation: ?Balanced equation: ?
2 KClO3 (s) 2 KCl (s) + 3 O2 (g)
Ammonium nitrate, when heated, decomposes into nitrogen gas, oxygen gas, and water vapor. What is the sum of the coefficients in the balanced equation using smallest integer coefficients?
A) 3 B) 5 C) 7 D) 9
QUESTION
Ammonium nitrate, when heated, decomposes into nitrogen gas, oxygen gas, and water vapor. What is the sum of the coefficients in the balanced equation using smallest integer coefficients?
A) 3 B) 5 C) 7 D) 9
ANSWER
2 NH4NO3 (s) 2 N2 (g)+ 1 O2 (g) + 4 H2O (g)
Chemical Reactions
Single DisplacementSingle Displacement AB + C CB + AAB + C CB + A Example:Example:
• HCl HCl (aq) (aq) + Mg + Mg (s) (s) MgCl MgCl22 (aq) (aq) + H+ H22 (g)(g)
• Balanced Equation: ?Balanced Equation: ?
2 HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g)
Single Displacement(Oxidation / Reduction)
Write a balanced equation for the Write a balanced equation for the following reaction:following reaction:
Chemical Reactions
Double DisplacementDouble Displacement AB + CD AD + CBAB + CD AD + CB Example:Example:
• A solution of sodium phosphate reacts with A solution of sodium phosphate reacts with a solution of silver nitrate to produce a solution of silver nitrate to produce aqueous sodium nitrate and a precipitate of aqueous sodium nitrate and a precipitate of silver phosphate.silver phosphate.
• Balanced equation: ?Balanced equation: ?
Na3PO4 (aq) + 3 AgNO3 (aq) Ag3PO4 (s) + 3 NaNO3 (aq)
Chemical Equations
•Combustion:Combustion:
CC88HH18(l)18(l)+ O+ O2(g)2(g) CO CO2(g)2(g) + H + H22OO(l)(l)
Oxygen reacts with octane to produce carbon dioxide and water.Oxygen reacts with octane to produce carbon dioxide and water.
Reminder: the equation must balance:Reminder: the equation must balance:
2 C8H18(l)+ 25 O2(g) 16 CO2(g)+18 H2O(l) 16 CO2(g)+18 H2O(l)
ANSWER
2
D) 13
O should be balanced last since it contains only one type of element and balancing it will not cause an imbalance in another element.
2 C8H18 (l)+ 25 O2(g) 16 CO2(g)+18 H2O(l)
2 C4H10 (l)+ 13 O2(g) 8 CO2(g)+ 10 H2O(l)
Consider the molecular view of reactants converted to a product in the boxes shown below:
Which balanced equation best represents this reaction?
A) NO + Cl2 → Cl2NO B) 2 NO + Cl2 → 2 ClNO
C) N2 + O2 + Cl2 → 2 ClNO D) NO + Cl → ClNO
chlorine
nitrogen
oxygen
QUESTION