7.0 ml of 6.0 M NaOH are diluted with water to a volume of 400 ml. You are asked to find the molarity of the resulting solution. The total number of moles of NaOH is not changed on dilution. Calulate the molarity.

Question

Work: (6)(.007)=(x)(.4)
x=.105M

Thanks for showing your work. I wish more students would do that.

Since the new volume would be 407 ml, I would say
(6)(.007)=(x)(.407)
x=.103M

The problem states that 7.0 mL is diluted with water to a volume of 400 mL. So the 7.0 mL is included in the 400 and 400 mL is the final total volume. Therefore, the molarity is as first calculated of 0.105 M.