1. Read MISC 327, Graphical Representation of Data, in this series or another au

Question

1. Read MISC 327, Graphical Representation of Data, in this series or another authoritative source that describes the principles of graphing. (1) Using the graph paper on the next page, draw the cooling curve for nitrobenzene. (2) Determine the freezing point of nitroben Zene from the curve. 2. A student beginning this experiment accidentally spilled some tbutyl alcohol on his hands and on the laboratory bench. Describe any potential danger t situation might cause and state the proper methoo cleaning up from the accident. (3) On the same graph draw the cooling curve for the unknown solution composed of 50.0 g of nitrobenzene and 5.00 mL of the liquid unknown. (4) Determine the freezing point of the un- known solution. ########### (5) Determine the freezing point depression, 3. The freezing point depression of a solution of nitrobenzene and a nonionic unknown was used to determine the molar mass of the unknown. Time-temperature data for the cooling of nitroben- zene and for the cooling of a solution containing 50.0 g of nitrobenzene and 5.00 mL of a nonionic liquid un- known, are given below. The density of the unknown was 0.714 g mL-1.The Kof nitrobenzene is 6.87°C (6) Calculate the molality of the solution, me (7) Calculate the gram molar mass of the unknown. unknowrn time, min temp, time, min temp, °C 0.0 0.5 1.0 0.0 1.0 1.5 10.75 8.75 7.00 5.00 2.5 Briefly explain why it is absolutely criticalthat the test tube containing the sample of nitrobenzene be 1.25 4. absolutely dry when determining the freezing tem- perature of nitrobenzene -2.25 5.00 5.30 7.0 9.0 10.0 11.0 11.0 -2.00 -2.10 16.0

Explanation / Answer

1. The plot of temperature vs time is plotted here to determine the freezing point of the solution.

2. t-Butyl alcohol is an irritant and toxic if inhaled, therefore, immediately washing with lots of water in case of spill is advised. Proper medical attention is advised.

3. Kf for nitrobenzene = 6.87 oC/m

mass nitrobenzene = 50 g = 0.050 kg

mass unknown = 5 ml x 0.714 g/ml = 3.57 g

moles of unknown = 3.57/molar mass

(2) freezing point of nitrobenzene = 5.20 oC

(4) feezing point of unknown = -2.20 oC

(5) dTf = -2.20 - 5.20 = -7.40 oC

(6) molality of solution = 3.57/molar mass x 0.050

(7) Formula,

dTf = - i.Kf.m

i = 1 [non-ionic compound]

dTf = -2.20 - 5.20 = -7.40 oC

So,

-7.40 = - 1 x 6.87 x 3.57/molar mass x 0.050

molar mass of unknown = 66.30 g/mol

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.