Explain how each of the following errors would affect the determination of the m

Question

Explain how each of the following errors would affect the determination of the mass of the sodium chloride collected.

a.) The liquid level in the pipet was below the line of the pipet

b.) The pipet was washed with d.i. water before using but the student forgot to rinse the pipet with sodium chloride solution before pipetting the sample

c.) The student forgot to dry the outside of the pipet before delovering his/her solution to the evaporating dish

d.) The mass of the evaporating dish was recorded less than the true mass

Explanation / Answer

a) This is caused by parallex error. As the volume of NaCl solution is actually less than what is recorded, thus the true mass of NaCl that we get will also be less what the mass expected.

b) This will cause some water droplet, to remain inside the pipet. Now when NaCl solution is filled with it, this existing droplet will make the collected solution more dilute as compared to the actual solution concentration. Thus the collected NaCl mass again get reduced

c) As the outside is not dry, as a result moisture from the outer part, will again make the solution more dilute, and hence reduce the mass of the collected NaCl

d) As for calculating the mass, the mass of disk + NaCl is recorded from which the mass of the disk is substracted. If mass of the disk is recorded less, then it leads to increased recording to mass of NaCl.

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