Something that bugs me about concentration

[Hitman123]

This may sound ridiculous to the elite here, but if I had a bottle with 500mL of vinegar where 5% was acetic acid. If I removed 100 mL will there still be 5% acetic acid there then?

 

[DrClaude]

Hi Hitman123, welcome to PF!

Concentrations are relative quantities, so they do not change regardless of the volume (provided that the solution is uniform, or "well mixed"). So that 100 ml you remove will be 5% acetic acid, and the 400 ml left will be 5% acetic acid.

Think about it this way: if I tell you that 50% of a country's population is female, and ask you what percentage of the population of a given city in that country is female, what would you answer?