Titration

A quantitative experiment to determine the concentration of an acid or a base.

Let’s get started!

Step #1 – Rinse one buret with base, it is 0.1M NaOH(aq). Rinse another buret with the acid, it has an unknown concentration.

Fill’er up

Step #2 – Put the burets in a buret clamp and fill them just above 0.0ml.

Fill the tip.

Step #3 – To fill the tip of the buret, drain a small amount of each into a flask and then pour it down the drain.

Take some data

Step #4 – Record the value of each buret in your data table. Be sure to read the bottom of the meniscus.

Add some Acid

Step #5 – Rinse the flask with distilled water and then dispense about 10ml of the unknown HCl(aq). Be sure to record the exact amount of HCl(aq) remaining in the buret. Read the bottom of the meniscus

Time for some indicator

Step #6 – Add some phenolphthalein to the HCl(aq) in the flask. It should stay clear since phenolphthalein stays clear in an acid.

Titration time

Add base to the flask until the solution turns pink. At this point, you will have neutralized the acid. This is called the equivalent point.

Equivalent Point

Data, let’s take a closer look

NaOH(aq) HCl(aq)

0.1M unknown

7.5ml 10.0ml

This is the data collected, how do we determine the concentration of the HCl(aq)?

Go to the MOLE!!!

Use the molarity of the NaOH(aq) and the number of liters of NaOH(aq) to find the number of moles of NaOH(aq).

x moles

0.1M = -----------------

0.0075 liters

Cross Multiply Baby

When you cross multiply you now know that you used 0.00075moles of NaOH.

How many moles of HCl(aq) reacted with the 0.00075 moles of NaOH?

HCl + NaOH NaCl + HOH

Stoichiometry

That’s correct, since there is a 1:1 ratio of HCl to NaOH, we know that 0.00075 moles of HCl reacted.

0.00075moles NaOH x 1 moles HCl

1 mole NaOH=0.00075 moles HCl

What is the Concentration?

Molarity = moles/liters

0.00075 moles HCl

Molarity of HCl = --------------------------

0.01 liters HCl

= 0.075M HCl(aq)