Why does vinegar NOT have a constant boiling point?
Vinegar is not a pure substance...............
Vinegar is not a pure substance.........and is a solution of acetic acid in water at anything from say 5-20% (m/m) concentrations. We would not expect it to have a constant boiling point. To a first approx., its boiling point would be around the boiling point of water, but probably higher than that that of water.
Virtually the same temperature as water, i.e. just fractionally above 100 degrees Celsius.
Please note that vinegar is NOT acetic acid.
It is a very dilute solution of acetic acid in water, with concentration varying from roughly 4% w/w to around 20% w/w depending on whether it's the type you find in supermarkets, or the type used for industrial food production. So unless you know the actual concentration of acetic acid in the vinegar you cannot accurately state a boiling point.