A 30.84 cm3 volume of 0.128 M NaOH is required to reach the
phenolphthalein endpoint in the titration of a 5.441 g sample of
vinegar. Calculate the percent acetic acid in the vinegar. (Molar mass
of vinegar is 60.05 g/mol)
To calculate the percent acetic acid in the vinegar, we need to determine the number of moles of acetic acid present in the solution.
Step 1: Determine the number of moles of NaOH used.
The volume of NaOH used is given as 30.84 cm3, and the concentration is given as 0.128 M. To find the number of moles, we can use the formula: moles = volume (in liters) x concentration.
Converting the volume from cm3 to liters:
30.84 cm3 = 30.84/1000 L = 0.03084 L
Now, calculate the number of moles of NaOH:
moles of NaOH = 0.03084 L x 0.128 mol/L = 0.00395232 mol (approximately 0.004 mol)
Step 2: Determine the number of moles of acetic acid.
The balanced chemical equation for the reaction between acetic acid (CH3COOH) and NaOH is:
CH3COOH + NaOH → NaCH3COO + H2O
From the equation, we can see that 1 mole of acetic acid reacts with 1 mole of NaOH. Therefore, the number of moles of acetic acid is equal to the number of moles of NaOH used.
So, the number of moles of acetic acid = 0.004 mol.
Step 3: Determine the mass of acetic acid used.
The molar mass of acetic acid is given as 60.05 g/mol. To find the mass of acetic acid used, multiply the number of moles by the molar mass:
mass of acetic acid = 0.004 mol x 60.05 g/mol = 0.2402 g (approximately 0.240 g)
Step 4: Calculate the percent acetic acid in the vinegar.
The percent acetic acid can be calculated using the formula:
percent acetic acid = (mass of acetic acid / mass of vinegar sample) x 100
The mass of the vinegar sample is given as 5.441 g.
percent acetic acid = (0.240 g / 5.441 g) x 100 = 4.41% (approximately 4.41%)
Therefore, the percent acetic acid in the vinegar is approximately 4.41%.