<u>Answer:</u> The amount of sample left after 20 years is 288.522 g and after 50 years is 144.26 g
<u>Explanation:</u>
We are given a function that calculates the amount of sample remaining after 't' years, which is:

Putting values in above equation:


Hence, the amount of sample left after 20 years is 288.522 g
Putting values in above equation:


Hence, the amount of sample left after 50 years is 144.26 g
We use the following formula to calculate the number of atoms:
n (mol) = N(number of atoms) / NA
N(He) = n(mol) · NA
N(He) = 2,0 moles · 6.02·1023 = 12.04·1023 atoms
Answer: A material that readily transmits energy is a conductor, while one that resists energy transfer is called an insulator .
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The kinetic energy causes the air molecules to move faster and they impact the container walls more frequently and with more force. The kinetic energy of the gas molecules increases, so collisions with the walls of the container are now more forceful than they were before. As a result, the pressure of the gas doubles.