How do you find the molar mass of a volatile liquid lab?
If the substance in question is a volatile liquid, a common method to determine its molar mass is to use the ideal gas law, PV = nRT. Because the liquid is volatile, it can easily be converted to a gas. While the substance is in the gas phase, you can measure its volume, pressure, and temperature.
What is the most accurate way of measuring the molar mass of a volatile compound?
The Dumas method of analysis can provide a fairly accurate determination of molar mass. V is the volume in liters of the vessel in which the liquid is vaporized and T is the temperature in kelvins of the vapor.
What happens to the volatile liquid that is placed in the flask?
The flask is heated in boiling water. The liquid vaporizes, the vapors fill the flask and excess vapor leaves through the hole. Since the flask is open to the air, the pressure of the vapor will be the same as the atmospheric pressure. The gas temperature will be that of the boiling water.
What is the main source of error in the determination of the molar mass?
The primary source of error is in the mass measurement, which had a standard deviation of 1.5%. The method could be improved by using a more precise balance to decrease the error in the mass measurements. It is also interesting to note that the molar mass was found to be slightly smaller than the literature value.
What is the molar mass of volatile liquid?
number of moles = n = pV/RT . But we go one step further, because we will also measure the mass of the evaporated liquid. Knowing the mass and the number of moles will allow us to compute the molar mass of the liquid: molar mass = (mass)/(number of moles).
How does the Dumas method work?
The procedure entailed placing a small quantity of the unknown substance into a tared vessel of known volume. The vessel is then heated in a boiling water bath; all the air within the flask would be expelled, replaced by the vapor of the unknown substance.
What is the molar mass of the volatile liquid?
How does Dumas method work?
The Dumas method is one of the simplest ways to measure the molecular weight of a substance. It uses the ideal gas law. In this method we have to confine a sample of gas in a container of known volume, making sure when we do this that the sample is exactly at atmospheric pressure.
What is the molar mass of oxygen gas?
15.999 u
Oxygen/Atomic mass
What does a volatile liquid mean?
A volatile substance can be defined as (1) a substance that evaporates readily at normal temperatures and/or (2) one that has a measurable vapor pressure. The term volatile usually applies to liquids. The rate at which a substance vaporizes (volatilizes) under a fixed set of conditions is called the evaporation rate.
What factors determine the molar volume of liquids?
To calculate liquid molar volume and vapor pressure using equations of state, the data of critical temperature and pressure, acentric factor, and molar refraction are needed.
How do you calculate mole?
The mole represents a quantity of substance, but relates to the number of atoms or molecules rather than mass or volume. Specifically, 1 mole represents 6.022 x 10^23 atoms or molecules of substance. You calculate the number of moles by dividing the mass of substance by the substance’s atomic or molecular weight.
How do you calculate the mass of a mole?
Answer Wiki. In order to calculate the mass of one mole of a molecule, we must simply find the atomic weight of each atom in that molecule, multiply each by the number of times it appears, and add them all together.
How is molar mass determined?
Molar mass is determined by dividing the total mass of the substance which is the average masses of each atom by the amount in moles. The resulting figure will be grams per mole or kilograms per mole. The molecular mass is determined by calculating the mass of the substance as related to the 1/12th of carbon-12 isotope.