1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Finding volume of a solution using %W/V

  1. Nov 11, 2012 #1
    1. The problem statement, all variables and given/known data

    What volume of a 30% W/V hydrogen peroxide solution is required to prepare 425 mL of a 6.0% W/V solution?

    2. Relevant equations

    %w/v = (weight solute/volume solution) x 100%

    3. The attempt at a solution

    I'm not quite sure what to do because here I am given 2 percentages?
    %w/v = (weight solute/volume solution) x 100%
    Weight solute = (%w/v × volume solution)/100%
    = (30% × 0.425 L)/100%​
    = 0.1275 L ​

    Where to go from here and to apply this to the 6% solution?
  2. jcsd
  3. Nov 11, 2012 #2


    User Avatar
    Homework Helper
    Education Advisor
    Gold Member

    Biggest part of solving is to create the system of equations.

    Let v = volume of stock solution, the 30%.
    Let w = volume of just the water for dilution, 0% solute.
    You want total resulting solution 425 ml.
    425 = w + v.
    v + w = 425\,ml

    You are taking v ml. of stock 30% and diluting it to get 6%. Using decimal fractions instead of percent, you setup a ratio relationship:
    ((0.30)v)/(v+w) = 0.06
    [itex] \[
    \frac{{0.30v}}{{v + w}} = 0.06

    Two unknown numbers and two equations. Solve.
    Last edited: Nov 11, 2012
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook