compute volume and/ or weights of reagents to make the following solution.

Desired concentration: 40% NaOH + 4% Na2S2O3
Desired quantity: 1500 mL
Given: 90% w/w NaOH, pure Na2S2O3

I'm not sure how to do this so any help would be great. Thanks!

To compute the volume and/or weights of reagents needed to make the desired solution, we need to use the concept of mass/mass percent and the equation relating concentration, volume, and mass.

First, let's calculate the mass of NaOH needed:

Given:
- Desired concentration: 40% NaOH
- Desired quantity: 1500 mL

To calculate the mass of NaOH needed, we multiply the desired quantity by the desired concentration:

Mass of NaOH = Desired quantity * Desired concentration
Mass of NaOH = 1500 mL * 0.40 = 600 grams

Now, let's calculate the mass of Na2S2O3 needed:

Given:
- Desired concentration: 4% Na2S2O3
- Desired quantity: 1500 mL

Since pure Na2S2O3 is given, the mass percent is 100%. So, we can directly calculate the mass of Na2S2O3 needed:

Mass of Na2S2O3 = Desired quantity * Desired concentration
Mass of Na2S2O3 = 1500 mL * 0.04 = 60 grams

To summarize:
- To make the desired solution, you will need 600 grams of NaOH and 60 grams of Na2S2O3.
- Please note that these calculations assume that the volumes given (1500 mL) are for both NaOH and Na2S2O3. If these volumes are for each reagent individually, the calculations should be adjusted accordingly.