500 mL of He at 98 kPa expands to 750 mL. Find P2.

0.65atm or 65.3kPa

Explanation:

Given parameters:

Initial volume of He  = 500mL

Initial pressure  = 98kPa, this gives 0.967atm

Final volume  = 750mL

Unknown:

Final pressure  = ?

Solution:

A good grasp of Boyle's law should suffice here. The law states that:

 "the volume of a fixed mass of gas varies inversely as the pressure changes if the temperature is constant".

            Mathematically;

                P₁ V₁  = P₂ V₂

where P and V are pressure and volume

           1 and 2 are the initial and final states;

  Now, solve for the unknown P₂;

             0.967 x 500  = P₂ x 750

                   P₂  = 0.65atm or 65.3kPa

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

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