I distilled a solution consisting of propanone and water and recorded the boiling point of propanone depending on different concentrations. I thought that the boiling point elevation would be the appropriate theory here which means that the slope of the graph should be around 1.80 (ebullioscopic constant of propanone) but apparently, the slope is only around 0.15. Is there a reason for this and how can I explain the nonlinearity of the graph? Effect of morality of water on the change in boiling point of propanone

  • $\begingroup$ Convert the chart to quantities with expected linearity like $p_i=p_{i,0}x_i$. For ebulioscopic measurement the solute is expected nonvolatile. $\endgroup$
    – Poutnik
    Commented Feb 19, 2022 at 6:38
  • $\begingroup$ Additionally, if staying at ebulioscopic scenario of addition of water to propanone, you would use the constant for propanone, not water. $\endgroup$
    – Poutnik
    Commented Feb 19, 2022 at 7:52
  • $\begingroup$ Yes, I've made the changes but I still don't understand why the graph deviates so much. Is it because the solution is not ideal? why does it deviate to the right? $\endgroup$
    – Jay K
    Commented Feb 19, 2022 at 8:53
  • $\begingroup$ What is the quantity reported on the $Ox$ axis ? Is it the molality of water in the liquid to be distilled ? Is it the molality of the condensed vapor ? $\endgroup$
    – Maurice
    Commented Feb 19, 2022 at 9:21
  • $\begingroup$ Partly deviation (guessed) from the Raoult law, which is common, partly nonlinear dependence of b.p. on linear vapour pressure change. Linearity is just approximation for small changes. $\endgroup$
    – Poutnik
    Commented Feb 19, 2022 at 9:54


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