Gas Pressure – Converting Units of Measure    (Std 4c)


Converting units of measure for gas pressure is just like doing conversion of :

                        Mg  --->  g  --->  to  --->  moles  --->  atoms


            Review my tutorial on that in the tutorial:  Grams to moles to atoms - Tutorial or PDF


There are bridges for these conversions just as there were for those.  Everything is based on 4 basic equalities:

            1 atm = 760 mmHg

            1 atm = 760 Torr

            1 atm = 101,325 Pa

            1 atm = 14.69 psi


Converting from anything to anything else requires you to make one or all of the equalities above into fractions.  The top of the fraction will always be what you are converting to. 


            Example:     Convert 56 psi to atm’s.




                        56 psi         1 atm   

                        ------   x   ----------    =    3.81 atm

                            1           14.69 psi


Now let’s do an example of going through several steps:


            Example:   Convert  25,000 Pa’s to Torr.


                                        bridge               bridge


                        25,000 Pa          1 atm                   760 Torr

                        -----------  x   -------------   x   -------------   =    187.52 Torr

                              1                101,325 Pa            1 atm


Each bridge, or operation, is determined by where we start from and where we are going. 


If you want to check your work and see that you came out to the right answer, check out the conversion-calculator web sites, see which one you prefer:

Converter CALCULATOR – all types of units of measure conversions – applet  (Berkley)  

Converter for units of measure used in gas laws - USC


The odd problems do not have answers in the back of the book, but you can check them out with this little calculator.  All you have to do is put in the unit of measure you are starting with and then hit your tab key.  The calculator will give you all the other units of measure and their correct quantities.  To activate the calculator, click on “Click Here      You will find it on the left-hand side of the page ¾ of the way down.  After you activate the calculator enlarge it to full page.  Under the Type of Conversion (see upper left of screen), change the conversion type to pressure on the drop-down menu.  Now you’re ready to go.


Example:  using this calculator (link also shown above)

Converter CALCULATOR – all types of units of measure conversions – applet  (Berkley)  



Convert 25,000 Pa to Torr (see problem above and then check the answer I gave with the calculator.


      Click on Pascal as Original Units .   Next, enter 25,000 on the calculator keyboard.  The number you enter will be small and will be top center of the screen. 

Now click  torr in the New Units box.  Next, press Convert in the lower left of the screen.  Your answer in torr   will appear in the top center of the screen.             


                 187.516  which represents 187.52 when rounded.