Calculations for Chemistry is pHun!

Reminders

Complete these calculations before you come to lab.

You will not be able to start the experiment until you have completed the correct calculations and your TA has verified your buffer system.

Show all work so your TA can help you find your mistake.

Preparation

Access the PreLab assignment on Chem21labs.com. There you will find your assigned pH.

Value is between 1 and 8pH values are given in increments of

0.5 (i.e. 1.0, 1.5, 2.0, etc)

Preparation

Go to “Blackboard”, “Experiments” and find the table of available acids and salts.

Determine which acid/salt pair you should use to make a buffer with your assigned pH.The pH should be within ± 1 of the

pKa value of the acid. Find the concentration of the acid that

will be available.

Calculations

Use the dilution equation to determine the volume of your acid needed to prepare 100 mL of a 0.100 M solution

2211 VMVM

Calculations

Calculate the molar mass of the saltYour salt should contain the conjugate

base of your acidInclude hydrates (water molecules)

when calculating the molar mass

Calculations

Use the Henderson-Hasselbalch formula to calculate the concentration of your conjugate base The concentration of acid should be 0.100 M

[acid]

base] [conjugatelog pK pH a

Calculations

Use the concentration of base, the volume (100 mL) and the molar mass to calculate the mass of salt needed to prepare your buffer.