What is the equivalent formula weight of an unknown weak acid in g/mol will be determined in this experiment.

Question

The equivalent formula weight of an unknown weak acid in g/mol will be determined in this experiment. Calculate this value if it took 16.7 mL of 0.234 M NaOH to titrate or neutralize 2.222 g of the unknown weak acid.

Answer 1

Formula weight is measured in g/mol. You already know how many grams you have (2.222 g), so you need to calculate how many moles of your acid you have. Neutralization means you have the same number of moles of acid as you do base, so if you calculate the number of moles of base you will find the number of moles of acid:

16.7 mL x 1 L/1000 mL x 0.234 mol/L = 0.00391 mol NaOH, which means you also started with 0.00391 moles of your weak acid.

2.222 g of acid / 0.00391 mol of acid gives a formula weight of 568 g/mol.