© copyright 1995-2010 r.j. rusay general reactions dr. ron rusay

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

General Reactions

Dr. Ron RusayDr. Ron Rusay

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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

1

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

The Reaction of Sodium & Chlorine

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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)

1

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

General Chemical Reactions

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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):Balancing (Conservation of Atoms):• 22 H H2 (g) 2 (g) + O + O2 (g) 2 (g) -----> -----> 22 H H22O O (g)(g)

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

Synthesis of Water

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

An Unwanted Synthesis of WaterCombustion & the Hindenburg 1937

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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)

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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: ?

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

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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: ?

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

Single Displacement(Oxidation / Reduction)

�Write a balanced equation for the Write a balanced equation for the following reaction:following reaction:

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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: ?

© Copyright 1995-2010 R.J. Rusay© Copyright 1995-2010 R.J. Rusay

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)

QUESTION

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.

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

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

ANSWER