Experiment 5

Experiment 5: Flame test - Identification of Ions

Experimental objectives:

• Observe and understand why the different aqueous ionic solutions produced colored flames

• Identify composition of the unknown ionic solution

Learning Objectives: 

• Identify what elements are present in certain aqueous solutions

• Identify trends and patterns in groupings of solutions based on colors produced

Background/Theory

• Many elements emit colored light when their atoms are excited by external sources like heat or electric currents

• Each element has a unique atomic emission spectrum with different numbers and colors of lines

Procedure:

Bunsen Burner set-up:

• Turn on bunsen burner and adjust the fame so that there is small blue cone in the center (more centered heat)

Setting up the test:

• Clean and dry the watch glass

• Clean the loop of the nichrome wire by dipping it first in 1M HCl, then DI water and heat it in the burner flame (sanitize it of prior solutions)

• Repeat until wire has no color to the burner flame

Solution Color Analysis:

• Place a few drops of solution to be test on the watch glass, tilt the watch glass and hold it so the drops of solution are near the air vent of the burner

• Heat wire in the flame, dip it into the liquid on the glass to atomize the solution into the air uptake of the burner

• Observe color in the flame

(Repeat this with each solution while cleaning in between)

Analyzing data/observations:

• Group known substances based on color of the flame produced

• Based on the results for the known substances and the unknown solution, what can you conclude about the composition of the unknown?