Chemistry 1515L Week 7
Graduate Teaching Assistant
Contact Information
Standard Solutions: Titration
The use of M1V1 = M2V2 to calculate the concentration (molarity) of an unknown acid solution
• We make up a solution of NaOH of approximate concentration
• We use a burette to add a solution of HCl of exact concentration
• Use phenolphthalein as an indicator to find neutralization point
p
p
p
• This helps us find the exact concentration of the NaOH solution
• We then titrate that NaOH solution with unknown acid We then titrate that NaOH solution with unknown acid
• This helps us calculate the concentration of the unknown acid
Setting up the Burettes
• We
We use a burette clamp attached to the ring stand to use a burette clamp attached to the ring stand to
support the burettes
• Each
Each clamp with safely support two burettes, one for clamp with safely support two burettes one for
adding acid, the other for adding base
Making the NaOH Solution
• You
You will use the Florence flask to make up the approximate will use the Florence flask to make up the approximate
NaOH solution • Swirl the flask gently to make sure that the solution is well mixed Using the Burettes
• Pour liquids into burettes over the sink. DO NOT attempt to pour in solutions above your
pour in solutions above your eye level as this is very dangerous.
• Make sure the flow from the burette is reasonable and that the opening is not blocked.
p
g
• Make sure that the liquid does not splash out of the flask when dropping from the h d
i f
h
burette.
More on the Webpage
Using the Burettes
• Placing a piece of paper behind the burette will help you read the liquid level.
the liquid level.
• The bottom of the meniscus is the point at which you take the reading.
• Make sure you make readings at, or below, eye level.
,
, y
With phenolphthalein indicator, With
phenolphthalein indicator
adding the solutions will give a bright pink color as the titration progresses You are looking for
progresses. You are looking for the color to persist.
Calculations
The use of M1V1 = M2V2 to calculate the concentration (molarity) of an unknown acid solution
A copy of the modified Report Sheet is at the front of the lab
Make sure you write in the Unknown Acid number
y
Waste solutions may be washed down the sink with plenty of water
Waste solutions may be washed down the sink with plenty of water
For Next Lab Session:
• Read all of the material available related to the next experiment (Analysis of a Commercial Antacid).
• Email me with any concerns.