Calculate the mass of solid Na2S2O3•5H2O required to prepare 300. mL of 0.0200 M Na2S2O3
.3L of .02M solution contains .006 moles of solute.
So, take .006 * mol wt of solute to get the mass
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.
The problem asks for mass Na2S2O3.5H2O. You calculated mass Na2S2O3. Add the 5 mols H2O to find the mass of the hydrated salt.
To calculate the mass of solid Na2S2O3•5H2O required, we need to use the equation:
moles = molarity × volume
First, let's find the number of moles of Na2S2O3 needed:
moles = 0.0200 M × 0.300 L
To convert the volume from mL to L, divide it by 1000.
moles = 0.0200 M × 0.300 L/1000
Next, we need to convert moles of Na2S2O3 to grams using the molar mass of Na2S2O3•5H2O.
The molar mass of Na2S2O3•5H2O is:
2(22.99 g/mol) + (32.07 g/mol) + 3(16.00 g/mol) + 5(18.02 g/mol)
Calculate the molar mass and multiply it by the number of moles:
mass = moles × molar mass
Now, let's go through the calculations:
moles = 0.0200 M × 0.300 L/1000 = 0.006 moles
Now, let's calculate the molar mass:
molar mass = 2(22.99 g/mol) + (32.07 g/mol) + 3(16.00 g/mol) + 5(18.02 g/mol) = 248.18 g/mol
Finally, calculate the mass of Na2S2O3•5H2O:
mass = 0.006 moles × 248.18 g/mol
Therefore, the mass of solid Na2S2O3•5H2O required to prepare 300 mL of 0.0200 M Na2S2O3 is approximately 1.49 grams.