Aballoon vendor at a street fair is using a tank of helium to fill her balloons. the tank has a volume of 113.0 l and a pressure of 122.0 atm at 25.0 °c. after a while, she notices that the valve has not been closed properly. the pressure had dropped to 112.0 atm (the tank is still at 25.0 °c).

Given Data:
                   P₁  =  122 atm

                   P₂  =  112 atm

                   V₁  =  113 L

                   V₂  = ?

Solution:
              Let suppose the gas is acting ideally. According to Ideal gas equation, keeping the temperature constant,

                                  P₁ V₁  =  P₂ V₂
Solving for V₂,
                                      V₂  =  P₁ V₁ / P₂
Putting Values,
                                      V₂  =  (122 atm × 113 L) ÷ 112 atm
                 
                                      V₂  =  113 L

Converting Volume to Moles,
 As,
                         22.4 L is occupied by  =  1 mole of He gas
So,
                         113 L will occupy        =  X moles of He gas

Solving for X,
                                     X  =  (113 L × 1 mole) ÷ 22.4 L

                                     X  =  5.04 Moles of He 

All the elements are arranged by melting points on the periodic table. in row they go from metals to gasses. in the row from sodium to argon, sodium is more reactive than the one on its right, magnesium.