Calculate the mass of solid Na2S2O3•5H2O required to prepare 300. mL of 0.0200 M Na2S2O3

Answer 1

.3L of .02M solution contains .006 moles of solute.

So, take .006 * mol wt of solute to get the mass

Answer 2

ok.. that's what I had done before..

Na2s203 has a mass of 158.11g

so I get for 0.006 mol of Na2s203 = 0.9486 g or with 3 significant figures = 9.48 mg.

but this still comes up as wrong when I put it into my online portal for my lab.

Answer 3

The problem asks for mass Na2S2O3.5H2O. You calculated mass Na2S2O3. Add the 5 mols H2O to find the mass of the hydrated salt.