jonny008

Here's the instructions. The relevant parts are 3-7. The objective of this lab was to determine the Mass% of a liquid with an unknown quantity of salt by using the calibration curve we generated.

Well, that's the thing. Within the procedures manual it was clearly stated that we had to weigh first, then dissolve, and that pretty much seals the deal to make me think this isn't a trick question.\ Besides, the question was formulated as a "Why must you weight before mixing" instead of a "Must you weight before mixing", kind of implies there is not room of argument about this point. I can't really prove right or wrong because I didn't specifically weight and record the before and after mixing weights, but come on, that's common sense. Just because it's dissolved it doesn't become lighter.

This is from a post lab question. The lab was really easy. Basically we were graphing the relation of the density (y axis) of salt water and the concentration of salt in water (x axis) As you can imagine our graph looks like a relatively straight slope with it's intercept at 1 g/ml In one part of the test we had to weigh the beaker + water + salt combination SPECIFICALLY before mixing and dissolving the salt. The post lab question essentially asks me why must we weight this combination before it becomes dissolved. I don't get that, the weight doesn't change, it's still the same. Would our graph be any different had we mixed it before weighing? The only reason I can come up with is that it's technically not "salt" anymore but Na cations and Cl anions, but that seems kind of a longshot