Heptane and octane from ideal solution at 373k the vapour pressure of the two liquid components 105.2kpa and 46.8kpa respectivly if the solution contains 25g of Heptane and 35g of octane calculate 1.vapour pressure of heptane and octane 2.v.p.exerted by the solution 3.molefraction of octane in vapour phase

Asked by mayadesai | 6th Jul, 2013, 06:57: PM

Expert Answer:

Vapour pressure of heptane 

Vapour pressure of octane = 46.8 kPa

We know that,

Molar mass of heptane (C7H16) = 7 × 12 + 16 × 1

= 100 g mol?1

Number of moles of heptane =25/100

= 0.25 mol

Molar mass of octane (C8H18) = 8 × 12 + 18 × 1

= 114 g mol?1

Number of moles of octane

= 0.31 mol

Mole fraction of heptane,.25/(.25+.31)

= .448

And, mole fraction of octane, x2 = 1 ? 0.456

= 0.551

Now, partial pressure of heptane, 

= 0.488 × 105.2

= 51.34 kPa

Partial pressure of octane, 

= 0.551 × 46.8

= 25.79 kPa

Hence, vapour pressure of solution, ptotal p1 + p2

=  77.13kPa

Answered by  | 8th Jul, 2013, 01:01: AM

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