I don't understand what this term means:
"Vinegar must not be less than 4% by mass acetic acid."
I don't know where you found this quote but it means that vinegar, sold to the customer, must contain at leat 4 grams of acetic acid for each 96 grams of water. Does that help? I don't know if that is a FDA regulation or not.
thank you, i found this in my lab book.
I looked it up on an FDA site and found that vinegar MUST contain AT LEAST (it may contain more) 4% acid
The term "Vinegar must not be less than 4% by mass acetic acid" is referring to the minimum concentration of acetic acid that should be present in vinegar. Acetic acid is the primary component responsible for the sour taste and strong smell of vinegar.
To understand this term, you need to know that the concentration of a substance is usually expressed as a percentage by mass. In this case, it means that the amount of acetic acid in vinegar should be at least 4% of the total mass of the vinegar.
To determine the concentration of acetic acid in vinegar, you would need to know the mass of acetic acid present and the total mass of the vinegar. This information is usually provided on the label of the vinegar bottle or can be found in the product specifications.
If you are unsure about the concentration of acetic acid in a particular vinegar, you can use a laboratory method called titration to determine the exact amount. In titration, a chemical reaction is conducted between the vinegar sample and a standardized solution of a known concentration, called a titrant. By measuring the volume of the titrant required to react completely with the acetic acid in the vinegar, you can calculate the concentration of acetic acid in the vinegar using stoichiometric calculations.