Excess molar quantity

When we mix different liquids together, sometimes they react in a special way where they don't just add up like you'd expect. Instead, they combine in a way where there's more than you'd think. That extra amount is called the excess molar quantity. It's kind of like when you mix two different colors of paint together and you end up with more than you started with! And just like with paint, the excess molar quantity can be measured and used to figure out how the liquids are reacting and what might be happening on a molecular level.