posted by Michael on .
Nitric acid is commonly purchased as a 16 M solution, which has a density of 1.41 g/mL.
Convert this molarity to a) mass percentage, b) molality, c) mole fraction.
w/w= 1008.32/1410= 71.5%w/w
B)1410-1008.32= 401.88 --> 16molHNO3/401.32= 0.40m
C)71.5%w/w (1mol/63.02)= 1.13--> 1.13
100gSoln(1ml/1.41)= 70.92--> .113/.71= .16 mol frac
A and B are ok.
I think C is incorrect.
If the soln is 71.5%, then you are right that 1.13 mol HNO3.
100 g soln = 71.5g HNO3 = 2.85g H2O (I think you converted to volume).
Then XHNO3 = 1.13 mols HNO3/(1.13+2.85) = about 0.4 or so.
How did you obtain 2.85gH20?
I made two typos and did not show a step. Here it is in detail.
That should be 100g total - 71.5g HNO3 = 28.5 H2O.
mols H2O = 28.5/18 = 1.58
total mols = 1.58 + 1.13 = 2.71
XHNO3 = 1.13/2.71 = 0.417