1.Why the burette and pieptte should be washed with distilled water and the solution to be used but NOT the solution to be used and then distilled water?
2.Why the volumetric flask should be washed with distilled water only but NOT the solution to be used?
I think the no. of mole of the solution will be affected
as the total volume in volumetric flask remain unchanged(i.e 250cm³)
so why cannot wash with the solution to be used?
titation1
2006-12-26 6:37 pm
回答 (1)
2006-12-26 7:14 pm
✔ 最佳答案
1. Water remained in the burette / pipette decreases the volume of the solution actually added. With the extra amount of water, the solution added will be diluted, and thus its concentration will be lowered. This results in an underestimation of the concentration of the solutions. The titration result will not be reliable.2. Volumetric flask is used for accurate dilution. An exact amount (# of moles) of the solution (to be diluted) is mixed with water to the graduated mark. If the solution is used to wash the flask, more (moles of) solution will remain in the flask apart from the volume required.
But rinsing the flask with distilled water will have no impact on the # of moles of solution in the flask. It just increases the volume of the diluted solution which is desirable.
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