Classifying Reactions

Classifying Reactions

Fall 2020

Multiple Select

How can we tell a chemical reaction occurred?

Check all that apply:

• temperature change

• precipitate produced

• gas produced

• color change

• shape change

Let's review:

 $PbSO_4\left(aq\right)\ +NaCl\ \left(aq\right)\ \longrightarrow\ PbCl_2\left(aq\right)\ +\ Na_2SO_4\left(aq\right)$                     (reactants)              (yields)                (products)

Multiple Select

The three elementary states of matter are:

• solid

• plasma

• liquid

• gas

There are four ways we express what state of matter compounds in a reaction are taking:

• (s) Solid

• (l) Liquid

• (g) Gas

• (aq) Aqueous - a substance dissolved in water

There are two major

classifications of reactions:

Oxidation-Reduction (RedOx) and Double Replacement

RedOx Reactions

• Electrons are transferred from one reactant to another

• Oxidation number plays an important

  role

• There are multiple types of redox reactions

RedOx Types:

• Synthesis

• Decomposition

• Single replacement

• Combustion

Synthesis Reactions

• Synthesis reactions have two substances (usually elements) coming together to form one new substance.

• Skeleton formula: A + B 🡪 AB

• Example formula: 2Na + Cl₂ 🡪 2NaCl

• Imagine: Peanut Butter + Chocolate 🡪 Reese’s Cups

Decomposition Reactions

• Decomp reactions have one substance decomposing into two (or more) substances.

• Skeleton formula: AB 🡪 A + B

• Example formula: 2Ni₂O₃ 🡪 4Ni + 3O₂

• Imagine: Tacos 🡪 Meat + Shell + Cheese

Multiple Choice

What is the skeleton formula for a synthesis reaction?

• AB 🡪 A + B

• A + B 🡪 AB

Single Replacement Reactions

• Single replacement reactions an element + compound yield new element + new

  compound (an element is switching places)

• Skeleton formula: A + BC 🡪 B + AC

• Example formula: Li + AgCl 🡪 LiCl + Ag

• Imagine: Suzie and Bobby are a couple and she dumps him for Jessie

Combustion Reactions

• Combustion reactions involve an reaction in the presence of oxygen and--if

  hydrocarbons--produce CO₂ + H₂O

• Skeleton formula: C_xH_y + O₂ 🡪 CO₂ + H₂O

• Example formula: C₃H₈ + O₂ 🡪 CO₂ + H₂O

• Imagine: Burning gasoline in an engine

Double Replacement Reactions

• two compounds that re-arrange to form two new compounds

• two categories and both have specific features to look for when identifying

Double Replacement Types

• Precipitation

• Acid-Base

Precipitation Reactions

• Precipitation reactions involve everyone having a new “partner” and having a solid product with a (s), which means it is insoluble in water

• Skeleton formula: AB + CD 🡪 AD + CB

• Example formula: NaCO₃ (aq) + CaCl₂ (aq) 🡪 NaCl (aq) + CaCO₃ (s)

Acid-Base Reactions

• Neutralization reactions involve combining an Acid + Base to yield a Salt

  + Water

• Skeleton formula: HX + YOH 🡪 YX + H2O

• Example formula: H₂SO₄ + KOH 🡪 K₂SO₄ + H₂O

Multiple Choice

What kind of reaction is the following?

4Fe + 3O₂ → 2Fe₂O₃

• decomposition

• synthesis

• acid-base

• single replacement

Multiple Choice

What kind of reaction is the following?

Zn + 2HCl → H₂ + ZnCl₂

• single replacement

• combustion

• synthesis

• double displacement

Multiple Choice

What kind of reaction is the following?

CH₄ + 2O₂ → CO₂ + 2H₂O

• double replacement

• synthesis

• acid-base

• combustion