On mixing, heptane and octane form an ideal solution. At $373\; K$, the vapour pressures of the two liquid components (heptane and octane) are $105\; k\;Pa$ and $45\; k\;Pa$ respectively. Vapour pressure of the solution obtained by mixing $25.0\;g$ of heptane and $35\; g$ of octane will be (molar mass of heptane
= $100 g\; mol^{–1}$ an dof octane $= 114\; g\; mol^{–1}).$
