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 weights of reagents required to make the desired solution, we need to use the concept of mass-mass percent concentration. Here's the step-by-step process:

1. Calculate the volume of 40% NaOH solution:
To determine the volume of 40% NaOH solution required, we'll first assume that the solution is made up of only NaOH. Since the desired quantity is 1500 mL and the desired concentration is 40%, the volume of 40% NaOH solution can be computed as follows:

Volume of 40% NaOH = (Desired quantity × Desired concentration of NaOH) / Percentage of NaOH in the solution

Volume of 40% NaOH = (1500 mL × 40%) / 90%

2. Calculate the weight of 90% w/w NaOH required:
Since the NaOH available is in the form of 90% NaOH, we'll need to find the weight of NaOH required to make the desired 40% NaOH solution.

Weight of NaOH = Volume of 40% NaOH solution × density of NaOH × percentage of NaOH in the solution

Density of NaOH will either be given or can be found in a reference source.

3. Calculate the weight of Na2S2O3 required:
Since the Na2S2O3 provided is pure, it means its concentration is already 100%. Therefore, we can directly calculate the weight of Na2S2O3 required:

Weight of Na2S2O3 = Desired quantity × Desired concentration of Na2S2O3

Once you have performed these calculations, you will have the volume of 40% NaOH solution (from step 1), the weight of NaOH required (from step 2), and the weight of Na2S2O3 required (from step 3).