Molar Mass Lab

Molar Mass of a Volatile Liquid There are several ways to find the molar mass of a substance. One way, if the substance is a gas, is to use the Ideal Gas Equation to find molar mass. The standard equation reads PV=nRT where “n” is the number of moles present, “P” is the pressure (which is obtained by reading the barometric pressure of the room with the class barometer), “V” is the volume of the gas, “R” is the universal constant, and “T” is the temperature of the gas. The experiment’s objective is to calculate the experimental value of molar mass of a volatile liquid through the process of heating (to form a gas, and thus use the ideal gas law to calculate the molar mass), and compare the results to the accepted value for the analysis of accuracy. This can be achieved by substituting the mass of the substance over the molar mass of the substance for “n”: m/M=n. The liquid heated to a gas is methanol, which has an accepted value for molar mass of 32.05g/mol.
Materials:
500 ml Erlenmeyer flask 1000 ml beaker Hot plate Aluminum foil
Needle
Unknown liquid sample (CH3OH)
Ring stand and beaker clamp

Procedure:
1) Prepare 1000 ml beaker by filling with water and heat to boiling on the hot plate
11) Add more unknown and repeat experiment (if time permits)
12) Rinse flask and fill with water completely
13) Take the temperature to find density
14) Mass flask and water to find mass of water
15) Find volume of Flask

Data/Calculations Mass of the flask and cover | 169.2g | Pressure in mm Hg | 741.2mm Hg | Temperature in vapor (°C/°K) | 98.0 °C/ 371.0°K | Mass flask and Water | 759.3g | Mass Water in Flask | 509.1g | Temperature of Water in flask | 22.0°C | Density of Water | .99780g/mL | Volume of Flask | 591.4mL | Amount of methanol used | 5.0mL | Mass Flask and Methanol Gas | 169.8g | Mass Methanol Gas | .6g | Calculated Molar Mass of Methanol | 30g/mol | Accepted Value for Molar Mass | 32.05g/mol | Percent Error |