Titrations

What is the goal of titrations?

To determine the concentration of a solution with an unknown molarity

Steps of titrations:

Use a volumetric pipette to dispense a volume of the analyte; Add an indicator to the analyte. The indicator will be used to determine the equivalence point; Use a burette to add titrant to the analyte; Add titrant dropwise until a color change occurs

Draw a picture for this step: Use a volumetric pipette to dispense a volume of the analyte

Draw a picture for this step: Add an indicator to the analyte. The indicator will be used to determine the equivalence point

Draw a picture for this step: Use a burette to add titrant to the analyte

Draw a picture of this step: Add titrant dropwise until a color change occurs

Common applications of titrations:

Redox reactions and acid base reactions

Calculations involved in titrations:

M1V1=M2V2

What happens at the equivalence point?

Moles of analyte = moles of titrant

What is molarity?

Moles of solute over volume of solution in liters

Substance in flask w/ unknown molarity:

Analyte

Substance in buret w/ known molarity:

Titrant

What is titrant also called?

Standard solution

Where does the standard solution usually go?

Buret

Point in titration where flask solution changes color

Endpoint

Point in the titration where the moles of acid are equal to the moles of base or moles of titrant is equal to moles of analyte

Equivalence point

Common sources of error for titrations:

Overshooting titration, not using indicator, using incorrect indicator, cleaning and preparing buret incorrectly, reading buret incorrectly

What does overshooting the titration result in?

The concentration of the unknown solution in the flask appearing to be higher than it actually is

How to tell that we are overshooting the titration?

Too dark of a color at the end

Why does overshooting the titration result in the concentration of the unknown solution in the flask appearing to be higher than it actually is?

Because more titrant must be added

What does not using an indicator result in?

No perceivable endpoint

How to choose a correct indicator?

By making sure that pH at the equivalence point should be approximately equal to the pKa of the indicator

How to clean buret?

Rinse buret with distilled water, add a small amount of titrant to buret, swirl, and let it out through the stem

What is the consequence of improper cleaning of buret?

The titrant is more dilute, so the analyte will appear to be more concentrated than it is

How should buret be read?

From the bottom of the meniscus

How many decimals should buret readings have?

2

Species involved in acid-base vs redox titrations:

Acids and bases vs redox species

Reaction involved in acid-base titrations vs redox titrations:

Neutralization vs redox reaction

Indicators used in acid-base titrations vs redox titrations:

Weak acids and weak bases vs redox species themselves as self-indicators or redox indicators

Are acid-base titrations or redox titrations more common?

Acid-base titrations

Why are acid-base titrations more common?

They can take place between any form of strong or weak acid and base

Redox titrations are commonly seen among what?

d block elements