Dalton’s)Law)of)Par/al)Pressures)•  “The%total%pressure%of%a%mixture%of%gases%is%equal%to%the%sum%of%the%partial%pressures%of%the%component%gases”%

%•  In%another%words,%if%you%have%a%container%with%multiple%gases.%The%sum%of%the%pressures%of%each%individual%gas%will%equal%to%the%total%gas%pressure%inside%the%container.%

Ptotal = PA +PB +PC +...

PV -_ NRT Pn=PV MM -_dRpINZTZ

←ME'EF.

Dalton’s)Law)of)Par/al)Pressures)•  This%may%seem%obvious%because%this%applies%to%moles%too%

•  However,%this%does%not%apply%to%temperature%or%volume%(keep%this%in%mind!)%! %When%we%mix%two%gases%with%separate%temperatures,%the%temperatures%do%not%add%up%

! %When%we%mix%two%gases%with%separate%volumes,%the%volumes%do%not%add%up%

ntotal = nA + nB + nC +...

Dalton’s)Law)of)Par/al)Pressures)•  Using%Dalton’s%Law%of%Partial%Pressures%and%the%moles%relationship,%we%can%come%up%with%a%combined%equation:%

%•  ‘A’%can%mean%any%component%of%the%mixture%•  The%ration%on%the%right%is%called%the%mole%fraction%of%A%and%represents%the%amount%of%A%to%the%total%amount%of%gas%particles%

PAPtotal

=nAntotal

PA =nAntotal

Ptotal =ΧAPtotal

O

-

-

O

Dalton’s)Law)of)Par/al)Pressures)•  Example:%

! A%sealed%vessel%contains%2.0%moles%of%N2%and%3.0%moles%of%O2.%The%total%pressure%of%the%vessel%is%10.0%atm.%What%is%the%partial%pressure%of%each%gas?%

I

PK NRT Pj÷=Pn2¥ MM -- DEI

Pto = Pnzt Poz ✓

htt = nnrztnoz } F÷EYT*SOP

:m - 40mm

pa=n±p35¥ . = 6.oatm

not

Dalton’s)Law)of)Par/al)Pressures)•  Partial%pressure%of%a%gas%is%proportional%to%the%amount%of%the%substance%in%moles.%%

•  Dalton’s%law%indicates%the%partial%pressure%of%a%gas%it%not%proportional%to%the%mass%(grams)%of%the%substance.%

Dalton’s)Law)of)Par/al)Pressures)•  Example:%

! %4.0%L%of%argon%gas%at%2.00%atm%and%1.0%L%of%xenon%gas%at%1.00%atm%are%mixed%to%produce%a%2.5%L%mixture.%%• What%is%the%partial%pressures%of%each%gas%in%the%mixture?%%• What%is%the%total%pressure%of%the%container?%(Hint:%Constant%T%and%notice%that%V%is%not%additive%for%gas)%– Find%PAr%and%Pxe%using%P1V1=P2V2%for%each%– Use%Dalton’s%law%to%[ind%the%total%pressure%

Pj, =P¥z Ve Pip

+ fit → FixP,VE PzvzPz=

Dalton’s)Law)of)Par/al)Pressures)•  Example:%

! %4.0%L%of%argon%gas%at%2.00%atm%and%1.0%L%of%xenon%gas%at%1.00%atm%are%mixed%to%produce%a%2.5%L%mixture.%%• What%is%the%partial%pressures%of%each%gas%in%the%mixture?%%• What%is%the%total%pressure%of%the%container?%(Hint:%Constant%T%and%notice%that%V%is%not%additive%for%gas)%

Ptot ¥ 3.00 Atm why ? 3. Gatm

use Pith Pzvz Pz -- par.to#tm4e4=3.za!!+=JJpz--Pxe--d'0atzm.C4--O.40a