The vapour pressure, p, of nitric acid varies with temperature as follows: θ /^∘C 0

The vapour pressure, p, of nitric acid varies with...

Key Concepts

Vapor Pressure

Vapor pressure refers to the pressure exerted by a vapor in equilibrium with its liquid phase at a given temperature. It is a measure of a liquid's tendency to evaporate and increases with temperature. Understanding vapor pressure is essential in studying phase transitions and thermodynamic properties of substances.

Normal Boiling Point

The normal boiling point is defined as the temperature at which a liquid’s vapor pressure equals the standard atmospheric pressure (typically 101.3 kPa). At this temperature, bubbles of vapor form within the liquid, leading to boiling. This concept is crucial for predicting and understanding the boiling behavior of substances under standard conditions.

Clausius-Clapeyron Equation

The Clausius-Clapeyron equation describes the relationship between vapor pressure and temperature, establishing that the natural logarithm of vapor pressure is linearly related to the inverse of temperature. This equation is instrumental in determining the enthalpy of vaporization and other thermodynamic properties by relating temperature changes to changes in vapor pressure.

Enthalpy of Vaporization

The enthalpy of vaporization is the amount of energy required to convert one mole of a liquid into vapor at its boiling point, under constant pressure. It represents the latent heat needed for phase transition and is a key parameter in the study of energy changes during vaporization, influencing both industrial processes and theoretical thermodynamic calculations.

Transcript

00:01 Alright, so for solving this problem let's first remember the two versions of the claus -clapeyron equation that we can find.

00:08 So the first one is useful, is this one.

00:12 It is useful when we have a lot of data points where we have the vapor pressure of a system and different values for temperatures.

00:20 And with this we can determine in an experimental way the value for delta h of vaporization.

00:25 Let's remember that in this case this looks a lot like y equals mx plus b, where y is going to be the logarithm of p.

00:34 This loop is going to be minus delta h of vaporization divided by r, and x it is going to be 1 over t.

00:40 And the value for c, it is going to depend on the units that we have for the pressure and we really don't have a use for the constant in this case.

00:51 It doesn't have like a physical value that we can take some information about.

00:57 So the first step that we are going to do is copy the data points, the values for temperature in celsius, convert all of them to kelvin, then the pressures we are going to take the logarithms of p, and finally the temperatures we are going to take the values for 1 over t.

01:17 With this we are going to be able to build a plot like this, with charts scattered, where we are going to select the data and in the x values we are going to take the values for 1 over t, and in the y values we are going to take the values for logarithm of p.

01:35 After that you can find, for example here, you are going to have an option to generate a trendline, we are going to set up a linear trendline and we need to display the equation that we find.

01:50 And as we mentioned, the value for the slope, it is going to be equal to minus delta h of vaporization divided by r.

01:58 So the enthalpy of vaporization is going to be equal to minus the values for the slope times r, r constant.

02:06 The units that we are going to have on delta h are going to depend on the units that we have on r, so here i am using r in joules per mole kelvin, which is 8 .314, and the value that we find with this is, for delta h, is simply multiplying this cell times minus r.

02:31 So this is going to be our final value for delta h of vaporization.

02:36 Now you may wonder why we did this first instead of finding in the very beginning the values for the normal boiling point, and the answer is because we didn't knew the value for the enthalpy of vaporization, thus there is no way for us to be able to solve the second part of the problem.

02:55 So once we have gone through that in this scenario, we are now able to get the normal boiling point.

03:03 Remember that the normal boiling point is when the pressure, the vapor pressure of the system, it is going to be equal to the atmospheric pressure...

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