When preparing a recognized mass of somepoint (e.g. once producing a traditional solution) it is frequently that in my school lab that we first usage a weighing watercraft to meacertain the mass and then once moved right into a beaker we reweigh the watercraft and calculate the mass transferred.

Do we this also though we zero the scale anyway?

Now to my understanding would this not boost the uncertainty as rather of just making use of the beaker on the range and adding the mass directly which would cause one uncertainty we rather weigh it twice which would therefore have actually 2x the uncertainty in the range.

Could somebody define wbelow my thinking is wrong and why this approach is even more accurate?

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edited Jun 24 "17 at 1:47

Anvarious other.Chemist
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asked Jun 23 "17 at 19:20

Jake RoseJake Rose
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Although tright here are numerous sources of weighing error that would be minimized by making use of the weighing by difference method (as discussed in the comments), I desire to illustrate what I watch as the limiting difficulty, that of the family member uncertainty of the measurement, which around scales (no pun intfinished, really) via the mass being measured.

Lets usage a bit of an exaggerated situation for illustration. In specific, we"ll say that we have actually one balance that have the right to meacertain dvery own to \$pu0.001g\$, and deserve to handle as much as \$pu100g\$ complete mass. In fact you would likely have actually a high-mass balance for weighing directly right into the beaker, or a low-mass balance for making use of the weighing watercraft. We are just using one really good balance to simplify this illustration, yet the concept is the exact same either means.

Lets say our beaker has actually a mass of \$pu50g\$, our weighing watercraft is \$pu1g\$, and also we are to meacertain out \$pu1g\$ of product.

The beaker plus the material to be measured will then have actually a measured mass of ~\$pu51.00 +/- 0.05g\$. This means that the relative uncertainty in the measured mass of the material is no much better than \$pu5\%\$(\$pu0.05g\$ out of \$pu1g\$).

The weighing boat plus the product to be measured out will have a measured mass of ~\$pu2.000 +/- 0.002g\$. This indicates that the relative uncertainty in the measured mass of the material is \$pu0.2\%\$ (\$pu0.002g\$ out of \$pu1g\$).

So, also with two dimensions fairly than one, using the weighing boat strategy results in a lot much less complete uncertainty in the measured mass of your material as compared to weighing a small amount of product straight right into a big beaker.