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Why is the vapour pressure of liquid con...

Why is the vapour pressure of liquid constant at a constant temperature ?

Text Solution

Verified by Experts

`P_(t)= P_(A) + P_(B)`
`P_(t)= P_(A)^@chi_(A) + P_(B)^@chi_(B) = 700chi_(A) + 300 (1-chi_(A))` …..(i)
=`300 + 400chi_(A)`
`chi_(A)^(V)=p_(A)/p^(t)=(700chi_(A))/(300 + 400chi_(A))=(7chi_(A))/(3 + 4chi_(A))`
`chi_(B)^(V)=p_(A)/p^(t)=(300chi_(B))/(300 + 400chi_(A))`=(`300(1-chi_(A)))/(300 + 400chi_(A))`=(`3-3chi_(A))/(3+4chi_(A))`
Put value in Eq. (i)
`500=700((7chi_(A))/(3+4chi_(A)))`+`300((3-3chi_(A))/(3+4chi_(A)))`
`:.chi_(A) =0.3,chi_(B)=0.7`
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