Question

Calculate the mass of non volatile solute with molar mads 40,which sould be dissolved in 114 g of octane to reduce vapour pressure to 80%

Answer 1

Ps=80% of P0=0.80

Solute =W40gmol−1

Solvent (octane)=114g114gmol−1

(molar mass of C8H18=114gmol−1)

Now P0−PsP0=x2

∴P0−0.80P0P0=W40W40+1

Or 0.8W40=0.2

⇒W=10g

I hope its helpful to you