A sample of krypton gas contains 2 x 10^25 atoms of Kr. What is the volume of this sample of gas at STP?

Question

please show equations. thank you

Answer 1

Find the number of moles using Avogadro's number :

(2. x 10^25 atoms Kr) x (1 mole Kr / 6.02 x 10^23 atoms Kr) = 33.2 moles Kr

At STP, 1 mole of any gas has a volume of 22.4 L , so the conversion factor to use is

(22.4 L Kr / 1 mole Kr STP) and the calculation is

volume = (33.2 moles Kr) x (22.4 L Kr / 1 mole Kr STP) = 744.2 L

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I have to admit I am stumped on how many significant figures to use in the final answer.

My understanding of sig. figs says that the answer must have the same number of s.f. as the given information. In this question, the given info is 2 x 10^25 , which has only 1 s.f., therefore I tend to think that my final answer should also be rounded to 1 s.f., or to 700 L .