A laboratory group measures an excess of an unknown liquid. They add this to an

Question

A laboratory group measures an excess of an unknown liquid. They add this to an empty flask for which they calculate the volume. They heat the sample n a water bath until al liquid has been vaporized tor several minutes. The sample is cooled and measured. Use their laboratory data (listed below to answer the following questions Use the appropriate number of significant figures in your answer. It is recommended each calculation is done in completion to ensure your answer is within the tolerance accepted. Do NOT use scientific notation to report answers in this question. 100.0+100.079.1 ml- Flask Volume mL Mass of flask Mass of Flask+ volatile liquid Mass of volatile liquid Temperature of water bath (c Pressure in lab (atm) Gas Constant 171.11g 171.31 g 0.20g 95.6 C 0.938 atm 0.00206 (L atm)mol K) Calculate the mol of gas in the flask using the ideal gas law: mol How many significant figures should you have reported in the above number of mol? Select an answersigniticant figures needed, Calculate the molar mass of gas in the flask gmol How many ignificant figures should you have reported in the molar mass? Select an answer significant figures Pcints possible: 4

Explanation / Answer

Flask V = 100+100+79.1 = 279.1 mL

B)

mol of gas

PV = nRT

n = PV/(RT)

n = (0.938)(279.1 /1000)/(0.082*(95.6+273.15)

n = 0.00865 mol

C

sig fig required -->

mass sig fig = 5; mass volaitel --> 2, T --> 2, V = 3 sig fig, P = 3 sig fig

report up to 3 sig fig --< 0.00865 --> 0.00865  mol

d)

molar mass = mass /mol = 0.20 / 0.00865 = 23.1213 g/mol

report up ot 2 sig fig, since 0.20 g has only 2 sig fig --> 23.1213 --> 23 g/mol

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