943 words - 4 pages

There are many concepts explored throughout “Enthalpy Vaporization of Water”.

First of all, the purpose of this lab was to determine the water’s vapor pressure at different temperatures as well as to measure the molar heat of vaporization of water using the Clausias Clapeyron equation. The first concept out of many represented in this lab is the ideal gas law. The ideal gas law is used to get the number of moles of air trapped in the 10 mL graduated cylinder. Once we cooled the system so that water vapor is extremely minute, and then we determined the number of moles of air using the ideal gas law. The number of moles of air equals to the pressure (in atm) times volume divided by constant times temperature. One would assume that when the water is heated to 80 degrees, the number of air molecules in the air bubble would decrease, but it actually stays constant. This is due to the fact that there is no air coming in or out of the cylinder. As the temperature gets closer to 80 degrees, the number of air molecules stays the same but the water vapor increases. And the bubble expands to keep the pressure at the same level. The ideal gas law was also used when the partial pressure of air in the gas mixture is calculated. This is gotten from number of moles multiplied by the constant and the constant and the whole thing divided by the volume.

Next Dalton’s law of partial pressure is used. The mixture of gas in the graduated cylinder was filled with two things: water vapor and air. Using the Dalton’s law, it can be concluded that the total pressure is equal to the pressure of air and the pressure of water vapor added together. This is an endothermic reaction which means that it absorbs heat, and when a reaction gains heat, it is represented to have a positive enthalpy.

One of the main concepts explored in this lab is the enthalpy of vaporization. The enthalpy of vaporization is dependent on the strength of the intermolecular gases. This represents how much energy that is required to convert the volume of liquid to that of its gas. This is gotten by using Clausius Clapeyron Equation. This equation shows the correlation between vapor pressure of a liquid and the temperature of that same liquid in Kelvin. When the dependency of natural log of water vapor pressure on the inverse of temperature is graphed, it shows a straight line. Using the Clausius Clapeyron Equation, the slope of the line can be retrieved. The slope equals to the negative of enthalpy of vapor divided by R constant which is 8.314 J/K·mol.

For error analysis, there were assumptions made in the experiments that...

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