Adisposable tank of helium can be purchased to fill up balloons. such tanks hold about 422 liters of helium compressed to 17.7 atm at room temperature (or 393k), and cost about $50. use the ideal gas law (pv = nrt) to calculate the number of moles of helium gas in the tank. for these units of pressure and volume, r = 0.0821 atm l/mol k.

Ascientist wants to know how individual lions within a pride interact with each other in their own environment. to do this, the scientist sedates and tags all of the lions within a pride. then, he places several remotely-controlled video cameras near the lions' den and performs an observational field study. he collects continuous video footage over the span of one year, analyzes the video, and then forms conclusions based on his observations.