When used correctly, the volumetric flasks in the first year chemistry laboratory will produce a solution volume of 250.00 ± 0.12 mL.
Calculate the concentration of the resulting solution at the three volumes below, if 6.14 g of ammonium persulphate, (NH4)2S2O8, is dissolved in water in this type of flask.
Molar mass of (NH4)2S2O8 = 228.18 g/mol
a. Concentration at 250.00 - 0.12 mL
b. Concentration at exactly 250.00 mL
c. Concentration at 250.00 + 0.12 mL
True of False: These results suggest that the mass of ammonium persulphate, (NH4)2S2O8, only needs to be weighed accurately to two decimal places, given the accuracy of the final solution volume.
sorry, not sure I understand. the mass of persulfate should be weighed to only two decimal places then?
mols (NH5)2S2O8 = g/molar mass = 6.14/228.18 = ?
M = mols/L solution
a. volume = 250.00 mL -0.12 mL = 249.88 = 0.25988 L
b. volume = 250.00 = 0.25000 L
c. volume = 250.00 + .12 = 250.12 mL = 0.25012 L
M = mols/L. You solve.
You may want to watch the number of significant figures.
ooops.
See this typo. There may be others. Check carefully.
a. volume = 250.00 mL -0.12 mL = 249.88 = 0.25988 L should be 0.24988.
By the way, I do wish you, whatever your name, would pick a screen name and stick to it. You could find us not answering your questions.
got it, thanks. ill keep it in mind for next time.
since, all of the answers rounded are the same, does that mean that the mass of ammonium persulfate should NOT be weighed accurately to two decimal places? instead, would need more decimal places to be more accurate?
I think you gave a true as well as a false for an answer.
You have a calculated M of
0.10758
0.1076
0.10768
So the calculated M is good to 1 in the 4th place. Why would you weigh the persulfate to only 1 in the second place?