Determining Molar Mass by Freezing Point Depression

A.P. ChemistryDetermining Molar Mass by Freezing Point Depression – Instructor Version5. Molality is calculated as followsmolality =moles of solutekg of solventUsing this equation and the rest of the data collected during this lab, calculatethe molar mass of benzoic acid from each trial and average them together.Report the average molar mass that was calculated. (4 points)0.819m =molar mass ofmoles ofmolarmass = 122.1Benzoic acid0.010 kg Lauric acidbenzoic acid =gmolso...grams ofmoles ofmoles ofbenzoic acidbenzoic acidBenzoic acid = 0.00819 mol1.0 g benzoic acidso... molar mass =0.00819 molesThe other trials are calculated in the same manner and then the results are averaged. The actualgmolar mass of Benzoic acid is 122.12 mol .Conclusion1. Look up the molecular mass of benzoic acid and compare it with theexperimental value. Calculate the percent error in the experimental molarmass. (2 points)122.12 − 122.1% error = × 100 = 0.016%122.122. Give a possible explanation that accounts for the error. (1 point)Possible sources of error include the scientific error involved in reading the scales,thermometers. Students may also include other sources of human error.3. If the benzoic acid were a strong acid that completely dissociated in waterforming H + ions and benzoate ions, what would have been the effect on thefreezing point. Give both a quantitative and qualitative response. (3 points)If benzoic acid were an ionic substance so that it would completely dissociate upon dissolvingin water, then the freezing point depression effect would be doubled because of the numberparticles in solution would be doubled. So the freezing point in trial one would actually be38.1°C. The ∆T for the other trials would also be doubled.