Anybody good at chemistry?

Question

I need help with the following problem:

You obtain the mass of an organic liquid "by difference" on an analytical balance using a 50.0 ml volumetric flask.  Your weights are 102.5608 g empty and 139.7432 g containing the 50.0 ml of the organic liquid.  A chemistry reference book gives the density for this organic liquid as 0.733 g/ml at the temperature of your measurements.  
         a) calculate the experimental density
         b) calculate your experimental percent error using 0.733 g/ml as the true density

Please explain work.  Thanks

Reginald · Accepted Answer

The mass (m) of the liquid is the difference between the weights of the full flask
and the empty flask; the difference equals the mass of liquid. So let's subtract:
139.7432 - 102.5608 = 37.1824 grams. The volume v is 50.0 ml, so the density
d = m/v = 37.1824 / 50.0 = 0.743648 gram per ml. (0.7436 g/ml to 4 significant
digits). The amount of error is the difference between your experimental density
and the true density, so the amount of error is 0.7436 - 0.733 or 0.0106 g/ml.
The percent you are off from the true density is equal to the amount of error
(0.0106) divided by the true density (0.733). 0.0106 / 0/733 = 0.01446 or 0.0145
rounded to 3 significant figures. In percent form this is 1.45 percent.

HPV · Answer

Density of liquid = mass of liquid / volume of liquid

Mass of liquid = 139.7432 g - 102.5608 g = 37.1824 g

Volume of liquid = 50.0 mL

Density of liquid = 37.1824 g / 50.0 mL = 0.744 g/mL


Percent error = ((your value - true value) / true value) x 100 = ((0.744 - 0.733) / 0.733) x 100 = 1.5%

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Anybody good at chemistry?

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