A student is making a solution of 0.1 M NaCl. The student adds 0.1 mole of NaCl to
the erlenmeyer flask and then adds 1 liter of water. Why is it important for the
student to make sure exactly 1 liter of water is added?
Because if the student doesn't add exactly 1 liter, then the molarity won't be 0.1
M NaCl.
Because it's important for the student to have enough solution.
It's not important -- as long as the student adds exactly 0.1 moles of NaCl, the
amount of water doesn't matter.
It's not important -- in fact it's wrong, because 1 liter of water will go over the
total amount of solution specified by the molarity.