Wyatt S.

asked • 10/02/14

How does contamination of water in a volumetric pipet affect density when calculating the density of an unknown substance?

Before getting to my question, I will state some background information that isn’t necessarily relevant to my question.

In our chemistry lab, we initially calibrated how much water we delivered on average with 25 mL volumetric pipets. We were able to calculate what the density of the water was from a given equation (involving room temperature). We then divided the mass of liquid delivered each trial by this density to approximate how much liquid was delivered on average.

The next phase of the lab involved finding the density of an unknown liquid using the approximated volume delivered that was calculated during the water phase of the lab.

Now, I’ve come to my question…

If several drops of water were to be left in the pipet from the first phase of the lab, would the true density of the unknown substance be affected, and if so, would it be higher or lower?
My initial thoughts are that since the volume isn’t being changed if this error were to go unnoticed, the answer lies in how the mass delivered from the pipet changes when the water mixes with the unknown substance. If the mass delivered were to be lower, than the density would be lower, and vice versa.

1 Expert Answer


Stanton D. answered • 10/06/14

4.6 (42)

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