Molecular Mass Lab
I. Purpose
The purpose of this lab is to determine the molecular mass of a volatile liquid.
II. Procedure
• Place a cork with a small hole in it inside of a test tube and find the weight of the two together using a sensitive balance.
• Pour 0.5 mL of the unknown volatile liquid into the test tube, insert the cork, and place the tube into boiling hot water while keeping the cork above water level. As the gas evaporates, excess gas will be released throughout the whole in the cork. Keep the test tube in the hot water for at least three minutes after all the liquid has vaporized and measure the temperature of the water.
• Quickly cool the test tube in an ice bath, dry it off and find the mass of the test tube, cork, and condensed liquid. …show more content…
While the outside of the test tube was dried, water vapor could have gotten inside the test tube through the hole in the cork. This water vapor could have condensed in the test tube and increased the mass of the test tube, cork and volatile liquid measurement. This increased measurement, since it is on top of the equation to find the molecular mass, would have produced a slightly higher molecular mass that the true. Also, the temperature of the gas was assumed to be the temperature of the boiling water. However, if the test tube wasn't heated evenly and part of it wasn't at the same temperature as the boiling water, then the actual temperature of the gas would have been lower than the temperature of the boiling water. Since the temperature is on the top of the equation to find the molecular mass, a falsely high temperature measurement would have resulted in a slightly high molecular mass …show more content…
Some of these are vaporization, volatility, condensation, molecular mass. The student uses vaporization to vaporize the unknown liquid in order to condense it later and then to find its mass so that it can be plugged into the calculations seen above to obtain the results that he/she obtained. Volatility in the context of this experiment is a measure of the tendency of a substance to vaporize. As the student observed the unknown liquid was actually volatile thus allowing the student to condense it and later obtain its molecular mass. Lastly, through the experimental process the student was able to find the molecular mass through several stoichiometric calculations as shown above.
VIII. Discussion Questions
1. How can the ideal gas law be used to determine the molecular mass of a liquid?
The liquid is heated and converted to a gas and the temperature, pressure, and mass are determined. The data is substituted into the Ideal Gas equation.
2. Was the vapor really “ideal?” If not, how would this affect the calculated molecular
The purpose of this lab is to determine the molecular mass of a volatile liquid.
II. Procedure
• Place a cork with a small hole in it inside of a test tube and find the weight of the two together using a sensitive balance.
• Pour 0.5 mL of the unknown volatile liquid into the test tube, insert the cork, and place the tube into boiling hot water while keeping the cork above water level. As the gas evaporates, excess gas will be released throughout the whole in the cork. Keep the test tube in the hot water for at least three minutes after all the liquid has vaporized and measure the temperature of the water.
• Quickly cool the test tube in an ice bath, dry it off and find the mass of the test tube, cork, and condensed liquid. …show more content…
While the outside of the test tube was dried, water vapor could have gotten inside the test tube through the hole in the cork. This water vapor could have condensed in the test tube and increased the mass of the test tube, cork and volatile liquid measurement. This increased measurement, since it is on top of the equation to find the molecular mass, would have produced a slightly higher molecular mass that the true. Also, the temperature of the gas was assumed to be the temperature of the boiling water. However, if the test tube wasn't heated evenly and part of it wasn't at the same temperature as the boiling water, then the actual temperature of the gas would have been lower than the temperature of the boiling water. Since the temperature is on the top of the equation to find the molecular mass, a falsely high temperature measurement would have resulted in a slightly high molecular mass …show more content…
Some of these are vaporization, volatility, condensation, molecular mass. The student uses vaporization to vaporize the unknown liquid in order to condense it later and then to find its mass so that it can be plugged into the calculations seen above to obtain the results that he/she obtained. Volatility in the context of this experiment is a measure of the tendency of a substance to vaporize. As the student observed the unknown liquid was actually volatile thus allowing the student to condense it and later obtain its molecular mass. Lastly, through the experimental process the student was able to find the molecular mass through several stoichiometric calculations as shown above.
VIII. Discussion Questions
1. How can the ideal gas law be used to determine the molecular mass of a liquid?
The liquid is heated and converted to a gas and the temperature, pressure, and mass are determined. The data is substituted into the Ideal Gas equation.
2. Was the vapor really “ideal?” If not, how would this affect the calculated molecular