Amixture of three noble gases has a total pressure of 1.25 atm. the individual pressures exerted by neon and argon are 0.68 atm and 0.35 atm, respectively. what is the partial pressure of the third gas, helium?
use mc031-1.jpg.

The partial  pressure  of the third gas (Helium)  is  0.22 atm

 calculation

Total pressure= partial pressure  for neon +  partial pressure for argon + partial pressure for helium

partial pressure for neon= 0.68 atm

partial pressure for argon = 0.35 atm

partial pressure for  helium = ? atm

make the partial pressure of helium the subject of the formula

Partial pressure of  Helium=  total pressure - ( partial pressure of neon +partial pressure for Helium )

=  1.25 atm - (0.68 +0.35 )  =0.22 atm

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"