# Question 1c0d4

Dec 12, 2014

The answer is $85.00 g$.

A solution's percent concentration is defined as the mass of solute divided by the total mass of the solution and multiplied by 100%.

c = (mass_(solute))/(mass_(solution)) * 100%, where

$m a s {s}_{s o l u t i o n} = m a s {s}_{s o l u t e} + m a s {s}_{w a t e r}$

Knowing that we have $100 g$ of solution, we can determine the mass of the solute by

m_(solute) = (c * m_(solution))/100 = (15.00 * 100.0)/(100%) = 15.00g

Therefore, the mass of water required for this solution is

${m}_{w a t e r} = {m}_{s o l u t i o n} - {m}_{s o l u t e} = 100.0 - 15.00 = 85.00 g$

This is a case where it is easy to eyeball the answer just because we are dealing with $100 g$ of solution...so a concentration of 20% would have required 80g of water and 20g of $H N {O}_{3}$, a concentration of 8%# would have required 8g of $H N {O}_{3}$ and $92 g$ of water, and so on...