If the student performs exactly two experiments and exactly one of the resulting two nonempty flasks contains an oran...

Skylar June 17, 2020

@Claudia-Frankel, your question seems to have been posted twice. I have attached @shunhe's response to your original post below for your reference:

"Thanks for the question! We have to use four flasks because of what we’re told in this question in the rules. First, we’re told that the student performs exactly 2 experiments. There are theoretically a number of ways to do this:

pour two unused flasks into two unused flasks
pour one unused flask into another unused flask. Then pour that flask into a third unused flask.

But we’re actually told in the first rule that the product of an experiment can’t be used in further experiments. In other words, we can’t pour the results of pouring one flask into another, into a third flask. So let’s look over this again.

Let’s say we pour flask 1 into flask 2. Now flask 1 is empty, and we can’t use flask 2, since it contains the products of an experiment. Which means flasks 3 and 4 have to be left for the last experiment. Which means that no matter what we do, we have to use all four flasks for the 2 experiments; we can’t just use 3 of the flasks.

Hope this helps! Feel free to ask any other questions that you might have."