40 g of liquid A and 70 g of liquid B are liquid B are mixed together to form ideal solution. Calculate the vapour pressures of liquid A and liquid B in vapour phase . Given ` , p _ A^@ = 200` mm , ` p _ B^@ = 700 mm`, ` M _ A = 56 g// mol `, ` M _ B = 90 g // mol `

Options

A. `P_(A)=0.208,rho_(B)=0.729`
B. `rho_(O)=0.479, rho_(B)=0.521`
C. `rho_(A)=0.714,rho_(B)=0.778`
D. `rho_(A)=0.7082, rho_(B)=0.829`

Answer

A

Explanation

` X _ A = ( 0.714) /( 0.714 + 0.778) = 0.479 `
` X _ B = ( 1 - X _ A) = 0.521 `
Now, ` p_A = p _ A^0 X_A = 200 xx 0.479 `
` = 95.8 ` atm
`p _ B = p _ B^0 X _B = 700 xx 0.521 = 364.7 ` atm
In vapour,
`p _A = ( p_A)/(p_A +p_B) = ( 95.8 ) /(95.8+ 364.7 ) `
` = 0.208 `
` therefore p _B ` (in vapour ) = ` ( 1 - 0.208 ) = 0.792 `