General Chemistry II Laboratory Manual, 2019 Revsion Questions: 39 5 When you set up the temperature probe using Capstone, you did not calibrate it to tead the correct temperature. It's possible that the probe reads temperatures that are consistently off by 1 or 2°C. Why won't this affect your results for this experiment? Explain your answer. four 2) What do you think is a source of error for this experiment? Do not answer "Errors in weighing or calculations." Sources of enron (orlld mc cold mc the foll oring. loss of sorute Through transferng, recording tempeiatines at wn the sorutron ngurou (to ensure a homugenoru i Solumon) and e Buigmg, contammamon Of T butan sufrent amnr of erren Imes, not STiring Sumple, nuA Obtainmy 3) If some t-butanol were lost between after it's weighed in before the first run, would the experimental molar mass of solute be affected? Explain your answer. how nores soute mne) xq soluent T=K( 13 lost in it sorvent werynt some heuw, ATA will mirease. This If scrvent 29 General Chemistry II Laboratory Manual, 2019 Revsion Determination of Molar Mass by Freezing Point Depression m= meres of Objectives: 1) To use freezing point depression to determine the molar mass of a solute. 2) To learn how to collect temperature data using computers. kg soluent Background: There are four colligative properties: osmotic pressure, solution vapor pressure, b ne point elevation, and freezing point depression. A colligative property is a property related to the concentration of solute particles in solution. If the solute does not dissociate in solution, colligative properties can be used to determine the molar mass of the solute. doent dissorrue.i In this lab we will use freezing point depression to determine the molar mass o an erganic compound. The change in the freezing point of a solvent is directly proportional ł (pam to the molality of the solute particles in solution. We will be using t-butanol (tertiary butanol, C4H9OH) as our solvent. The compound that we’ll use as a solute will nột dissociate easily in solution, which means that the molality of the solute will be tied directly to the number of molecules in solution, which makes it well suited for a molar mass determination. ec, m tred drrecrs to #moree ATB a m Dfp When a solvent or solution freezes, a çooling curve is observed and this can be used to 2) moral determine the freezing point of the solvent or solution. If temperature is plotted versus time when a solvent or solution is freezing, a plot such as the one shown below will an 3imw result. T but -) Sonvent od neo anoi Cooling Curve 35 34 33 32 31 30 29 28 27 tupere 26 450 400 350 300 250 200 150 100 time (s) At first there is a sharp drop in temperature. The drop in temperature becomes much less sharp when the solvent or solution begins to freeze. Sometimes the temperature will drop below the freezing point before freezing begins to occur. This is called supercooling, and has occurred in this particular plot. Temperature (deg C) 25