<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
<u>Answer:</u>
(A)
Density = Mass / Volume
So
Mass = Density × Volume


Mole ratio of toluene : Oxygen is 1 : 9

(B)
1 mole of Toluene produces 7 moles of
gas and 4 moles of
Vapour
So the mole ratio is 1 : 11

(C)
1mole contains
molecules

The answer is <span>Silicon, it also forms 4 bonds. Usually elements in the same group or vertical column in the periodic table all have similar chemical bonding properties. </span><span>It is just below carbon, so it has more similarities of properties with carbon. </span>