Reaction Types and Qualitative Analysis -

Technique Laboratory

Introduction

A wide variety of chemical reactions can be classified into a few types of chemical

reactions with different driving forces for what causes the reaction to occur. In

this laboratory we will look at a variety of different types of chemical reactions

and see how we can use some of those chemical reaction properties to identify

different compounds. Our previous labs have all been quantitative, meaning we

took measurements to determine precise values. This lab is a qualitative lab,

where we don’t need to worry about precise values and amounts. In a qualitative

lab, keen observations are key to being successful. Practicing scientists use

combinations of qualitative and quantitative observations to solve problems.

Building both quantitative and qualitative laboratory skills and knowing when to

utilize each skill set will help you grow as a scientist.

Observing Chemical Reactions

We can often see chemical reactions occurring by making specific observations

that utilize our everyday senses.

Observation 1: Color Changes

The formation of new chemical during a reaction can often produce new colors.

Changes in color associated with chemical reactions are most often observed

when a transition metal is involved in the reaction.

Observation 2: Formation of gases and smell

Gas evolution is often the driving force for a chemical reaction to occur. We can

see gas evolution reactions by seeing the bubbling of a gas. Even if we cannot

see a gas being formed, we can still check for properties of a gas being formed.

Testing a gas with a Lit Wooden Splint

A wooden splint (popsicle stick) can be lit with a match. If we place the lit splint

over a reaction that is occurring, we can see if a produced gas has any impact on

the lit splint. If the gas supports combustion (oxygen gas is a good example of

this), then the flame will glow brighter. If the gas is combustible (methane and

hydrogen are good example of this), then a quick “pop” is often heard. If the gas

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