calculationsforchemistryisphun
TRANSCRIPT
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.