he Food and Drug Administration (FDA) mandates that all vinegar sold in the United States must have a minimum concentration of 4% acetic acid by mass. Calculate the minimum molarity of acetic acid in vinegar according to this standard. Assume the density of vinegar is the same as for water.

We assume that we have 1 L of vinegar solution. Another assumption, as the problem says, is that the vinegar have the same density as water which is approximative 1000 g/L.

mass of vinegar solution = density * solution volume

mass of vinegar solution = 1000 * 1 = 1000 g

mass of acetic acid = (4 / 100) * solution mass

mass of acetic acid = (4 / 100) * 1000

mass of acetic acid = 40 g

number of moles of acetic acid = mass / molecular mass

number of moles of acetic acid = 40 / 60

number of moles of acetic acid = 0.66

molar concentration of vinegar solution = number of moles of acetic acid / solution volume (L)

molar concentration of vinegar solution = 0.66 / 1 = 0.66 M