# Calculate % Acetic Acid in Brand X Vinegar

• Numnum
In summary: Otherwise, %w/v is what you would need.In fact, the question in the original post is not completely clear. Volume percent is asked for. Therefore, you are right. The question is actually ambiguous. We are not given which unit is asked: %v/v or %w/v.
Numnum

## Homework Statement

A student wished to determine the percent of acetic acid in commercial vinegar products. Brand X was selected. Three 20.0mL volumes were titrated with a 2.20mol/L sodium hydroxide solution until the indicator phenolphthalein turned pink. The density of acetic acid is 1049.2kg/m3. The data gathered in the experiment is recorded below. Calculate the volume percent of acetic acid in vinegar.

Initial burette reading - Vi = 0.00mL
Volume reading first trial titration - V1 = 8.82mL
Volume reading second titration - V2 = 16.84mL
Volume reading third titration - V3 = 24.80mL
Concentration of the NaOH - c = 2.20mol/L
Volume of vinegar - Vvin = 20.0mL

## The Attempt at a Solution

I have done titration calculations before, but something about three titrations confuses me. I started with getting the mol of NaOH then using that to get the mole of acetic acid and from there using V3 to get the volume then dividing that by the volume of vinegar x 100%. I am not sure where to use the density.

Your numbers V1, V2, V3, are just buret readings. You find the individual titrant volumes of each titration by calculating the volume reading differences. Note also, you began at Vi = 0.00 ml. You should/could determine molarity of the acetic acid first; then find percent. You seem to be given density for the vinegar of about 1.049 grams per milliliter.

I have done titration calculations before, but something about three titrations confuses me. I started with getting the mol of NaOH then using that to get the mole of acetic acid and from there using V3 to get the volume then dividing that by the volume of vinegar x 100%. I am not sure where to use the density.

You do not need the density for percent w/v. You at least need the molecular weight of acetic acid.

I wonder what they meant by volume percent. w/v is not a volume percent and as symbolipoint mentioned it doesn't require information about density. v/v is a volume percent, but it requires two densities to be calculated. Given density is a density of a 40.4% w/w acetic acid solution, that's about eight times higher than concentration calculated from the titration result.

Last edited:
Borek said:
I wonder what they meant by volume percent. w/v is not a volume percent and as symbolipoint mentioned it doesn't require information about density. v/v is a volume percent, but it requires two densities to be calculated. Given density is a density of a 40.4% w/w acetic acid solution, that's about eight times higher than concentration calculated from the titration result.

The concentration as percent weight per volume simply means grams of solute per 100 milliliters of solution. One may use this kind of concentration if it fits ones purpose, or if ones laboratory supervisor expects it. (or if working certain textbook exercises).

symbolipoint said:
The concentration as percent weight per volume simply means grams of solute per 100 milliliters of solution. One may use this kind of concentration if it fits ones purpose, or if ones laboratory supervisor expects it. (or if working certain textbook exercises).

I know what w/v% is, I have no idea what the question asks about. Do you?

Borek said:
I know what w/v% is, I have no idea what the question asks about. Do you?

In fact, the question in the original post is not completely clear. Volume percent is asked for. Therefore, you are right. The question is actually ambiguous. We are not given which unit is asked: %v/v or %w/v.

Numnum, if you want %v/v, then from your found molarity, convert from moles to mass, and then use acetic acid density to convert from mass to volume.

## 1. What is the purpose of calculating the % acetic acid in Brand X vinegar?

The % acetic acid in vinegar is an important measure of its quality and potency. It can also be used to determine the concentration of other substances in the vinegar, such as flavor components and impurities.

## 2. How is the % acetic acid in Brand X vinegar calculated?

The % acetic acid in vinegar is typically calculated through a process called acid-based titration. This involves adding a measured amount of a strong base, such as sodium hydroxide, to a known volume of vinegar until the solution reaches a neutral pH. The amount of base used can then be used to calculate the % acetic acid in the vinegar.

## 3. What equipment is needed to calculate the % acetic acid in Brand X vinegar?

To perform an acid-based titration, you will need a burette, a standardized solution of sodium hydroxide, a pH indicator, and a known volume of vinegar. You may also need a beaker or flask to hold the vinegar and a stirrer to mix the solutions.

## 4. Can the % acetic acid in Brand X vinegar vary between different batches?

Yes, the % acetic acid in vinegar can vary between different batches due to factors such as the type of raw materials used, the fermentation process, and the storage conditions. This is why it is important to regularly test and monitor the % acetic acid in vinegar to ensure consistency.

## 5. Is there an ideal % acetic acid for vinegar?

The ideal % acetic acid in vinegar varies depending on its intended use. For culinary purposes, a range of 4-8% acetic acid is generally preferred. However, for cleaning or disinfecting purposes, a higher % acetic acid may be desired. It is important to check the label or manufacturer's instructions to determine the recommended % acetic acid for a specific use.

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