Chemical Reactions – Chapter 5

 

A chemical reaction is a well-defined example of a chemical change

 

n      Example

n      NaOH + HCl à NaCl + H₂O

 

n      Reactants are the starting materials for any chemical reaction

n      May be one or more substances

n      Written on the LEFT side of an equation

 

n      Example

n      NaOH + HCl à NaCl + H₂O

n      NaOH and HCl are reactants

 

n      Products are the ending materials for any chemical reaction

n      May be one or more substances

n      Written on the RIGHT side of an equation

 

n      Example

n      NaOH + HCl à NaCl + H₂O

n      NaCl and H₂O are products

 

n      Conservation of mass says that the total mass of the reactants must equal the total mass of the products

 

n      Mass of Reactants = Mass of Products

n      Example:

n      4g H₂ + 32g O₂ à 36g H₂O

n      Written with coefficients to “balance the equation” based on numbers of elements

n      2H₂ + O₂ à 2H₂O

 

Synthesis Reaction

n      When two or more reactants combine into one molecule

n      A + B à AB

n      2H₂ + O₂ à 2H₂O

n      Two people with similar interests meet and hang out for the rest of the day

 

Decomposition Reaction

n      When one reactant breaks into two or more products

n      Reverse of synthesis

n      CD à C + D

n      2H₂O à 2H₂ + O₂

n      Two friends are hanging out, then split up at the end of the day to go home

 

Single Displacement Reaction

n      When an atom from one molecule moves to another molecule

n      AB + C à A + BC

n      ZnO₂ + Cu à CuO₂ + Zn

n      Two friends hanging out, then one leaves to hang out with another friend

 

Double Displacement Reaction

n      When an atom from one molecule switches places with an atom from another molecule

n      AB + CD à AD + CB

n      NaOH + HCl à NaCl + H₂O

n      Neutralization is double displacement

n      Two couples switching partners at a dance