# How to Calculate Boiling Point From Vapor Pressure?

##### Joseph Hebert
Owner at - HVAC Buster

Joseph is an HVAC technician and a hobbyist blogger. He’s been working as an HVAC technician for almost 13 years, and he started blogging just...Read more

The boiling point of a liquid is the temperature at which it changes state from a liquid to a gas. The vapor pressure is the pressure exerted by the molecules of the liquid as they try to escape into the gas phase. The relationship between these two properties can be expressed by the Clausius-Clapeyron equation: ln(P2/P1) = (ΔHvap/R)(1/T2 – 1/T1).

This equation can be used to calculate the boiling point of a liquid if the vapor pressure is known.

## Calculating Vapor Pressure and Boiling Point

• Look up the boiling point of the liquid you are interested in on a reference chart
• Find the vapor pressure of the liquid at that temperature on the chart
• Use the formula: Boiling Point = Vapor Pressure * 760 / 101325 to calculate the boiling point from vapor pressure

## How to Find Vapor Pressure Given Boiling Point And Heat of Vaporization

Vapor pressure is the pressure of a gas above its critical temperature. The heat of vaporization is the energy required to change the state of a substance from a liquid to a gas. The boiling point is the temperature at which a substance changes state from a liquid to a gas.

To find the vapor pressure given these three pieces of information, use the Clausius-Clapeyron equation. The Clausius-Clapeyron equation states that: ln(P2/P1) = (ΔHvap/R)(1/T2 – 1/T1)

where P1 and P2 are the vapor pressures of the two substances being compared, ΔHvap is the heat of vaporization, R is the universal gas constant, and T1 and T2 are the temperatures in Kelvin at which P1 and P2 are measured. Solving for P2 gives:

## How to Find Boiling Point from Vapor Pressure Graph

If you need to find the boiling point of a substance from a vapor pressure graph, there are a few steps you need to follow. First, identify the horizontal line on the graph that represents the atmospheric pressure. This line will intersect the vapor pressure curve at two points.

The leftmost point is the boiling point at atmospheric pressure. The rightmost point is the critical point, beyond which the substance cannot be liquefied no matter how much pressure is applied. Next, locate the temperature where the vapor pressure curve intersects with your chosen atmospheric pressure line.

This is the boiling point of the substance at that particular atmospheric pressure. You can then convert this temperature to either Celsius or Fahrenheit using a scientific calculator or an online converter. Keep in mind that most vapor pressure graphs are only accurate for one specific type of atmosphere (e.g., sea level).

If you’re working with a different kind of atmosphere, you’ll need to find a graph that’s been specifically calibrated for that environment.

## How to Find Boiling Point from Vapor Pressure And Temperature

When it comes to finding the boiling point from vapor pressure and temperature, it’s important to understand the relationship between these two properties. Vapor pressure is a function of temperature, meaning that as temperature increases, so does vapor pressure. The boiling point is the temperature at which the vapor pressure of a liquid equals the atmospheric pressure surrounding the liquid.

One way to find the boiling point from vapor pressure and temperature is to use a steam table. A steam table lists the saturated vapor pressures of water at various temperatures. To use a steam table, simply find the temperature that corresponds to your desired vapor pressure on the left-hand side of the table.

The corresponding boiling point will be listed on the right-hand side of the table. For example, let’s say you wanted to know what the boiling point of water would be if its vapor pressure was 200 mmHg. Checking the steam table, you would find that at 200 mmHg, water boils at 94°C (201°F).

If you don’t have access to a steam table, don’t worry – there are other ways to calculate boiling point from vapor pressure and temperature. One such method is known as Riedel’s Law. This law states that for every substance, there is a linear relationship between log10(vapor Pressure) and 1/temperature (in Kelvin).

In other words, if we plot log10(vapor Pressure) against 1/temperature on a graph, we should get a straight line. From this straight line, we can then calculate both slope and intercept values which can be used to determine boiling point from either vaporpressure orTemperature using Riedel’s Law Equation: Boiling Point = 10^(Intercept) * Temperature^(-Slope) . Let’s try this out with an example.

Let’s say we want to know whatwater’sboilingpointwouldbeifitsvaporpressurewere200mmHgagain.(Recallthatfromthesteamtablewefoundit tob94°C.) To useRiedel’sLawweneedtocalculatethelog10of200mmHg=2log102+log10200=2+2=4 .

Nowlet’splotthisvalueoflog10(vaporpressure)=4onthegraphagainst1/temperature inKelvin .

## Boiling Point And Vapor Pressure Relationship

When a liquid is heated, its molecules gain energy and begin to move faster. Eventually, the molecules have enough energy to overcome the attractions that hold them together in the liquid state, and they enter the gas state. The temperature at which this occurs is called the boiling point.

The vapor pressure of a liquid is the pressure exerted by its vapor on the walls of its container. As a liquid is heated, its molecules gain energy and begin to move faster. At some point, they have enough energy to escape from the surface of the liquid into the gas phase.

The Vapor Pressure increases with temperature as more molecules are able to escape into the gas phase. The relationship between vapor pressure and boiling point can be illustrated using a diagram called a phase diagram (Figure 1). The horizontal axis represents temperature and the vertical axis represents vapor pressure.

The blue line shows how vapor pressure changes with temperature for water. At 0°C (the freezing point of water), the vapor pressure of water is about 0.03 atmospheres (atm). As you can see from Figure 1, very little change in vapor pressure occurs over this range of temperatures; thus we say that water has a fairly constant boiling point at atmospheric pressure.

When water reaches 100°C (its boiling point at standard atmospheric pressure), however, something remarkable happens: Its Vapor Pressure suddenly increases dramatically! In fact, at 100°C water’s Vapor Pressure is about one atmosphere—equal to atmosphericpressure itself! This means that if we continue to heat water beyond its boiling point at standard atmospheric pressure, it will boil vigorously and all of it will eventually turn into steam—regardless of whether or not there is any air or other gases present above it!

## How to Find Vapor Pressure from Temperature

Vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. The higher the temperature, the higher the vapor pressure. For example, water has a very low vapor pressure at room temperature (25°C), but its vapor pressure increases rapidly as the temperature is increased.

At 100°C, water’s vapor pressure is approximately one atmosphere (101.325 kPa). There are several ways to find the vapor pressure of a substance as a function of temperature. One way is to look up values in a reference book such as The CRC Handbook of Chemistry and Physics.

This book lists the vapor pressures of many common substances at various temperatures. Another way to find out how vapor pressure changes with temperature is to conduct an experiment. In this type of experiment, a known amount of liquid is placed in an enclosed container with a Thermocouple or other type of Temperature sensor .

The container is then heated at a constant rate while monitoring the change in Vapor Pressure . As theTemperature sensor measures an increase in temperature,the Vapor Pressure will also be seen to increase on your laptop or desktop computer that you have connected to your lab equipment via USB cable and software . After conducting this experiment, it would be useful to plot your data so that you can see how Vapor Pressure varies with Temperature .

You could use Excel or some other graphing program to do this easily. If you don’t have access to any reference books or experimental data, you can still estimate the relationship between Vapor Pressure and Temperature using kinetic molecular theory . This theory states that molecules are in constant motion and that they collide with each other and with surfaces.

When two molecules collide, they bounce off each other like billiard balls .

## How Do You Calculate Boiling Point Using Vapor Pressure?

To calculate the boiling point of a liquid using vapor pressure, you first need to know the vapor pressure of the liquid at various temperatures. This can be determined experimentally or by using a vapor pressure chart. Once you have this information, you can use the Clausius-Clapeyron equation to determine the boiling point.

The Clausius-Clapeyron equation states that: ln(P1/P2) = (ΔHvap/R)(1/T1 – 1/T2) Where P1 and P2 are the vapor pressures of the liquid at temperatures T1 and T2 respectively, ΔHvap is the heat of vaporization, R is the universal gas constant, and ln is the natural logarithm.

By rearranging this equation, we can solve for T2, which will give us the boiling point at a given vapor pressure:

## How Do You Calculate the Boiling Point?

When calculating the boiling point of a substance, you must first determine the atmospheric pressure. This can be done using a barometer. Once the atmospheric pressure is known, you can use a boiling point elevation chart to find the boiling point of the substance at that pressure.

The boiling point elevation chart shows the relationship between atmospheric pressure and boiling point.

## How Do You Find the Boiling Point of Heat Using Vaporization?

When you want to find the boiling point of heat, you need to use vaporization. This is because when a liquid boils, it turns into a gas. The boiling point is the temperature at which this happens.

To find the boiling point using vaporization, you will need to have a container of water and a thermometer. Place the thermometer in the water and turn on the heat. As the water starts to boil, you will see the thermometer reading start to rise.

When it reaches 100 degrees Celsius (212 degrees Fahrenheit), that is the boiling point.

## Is Vapor Pressure Same As Boiling Point?

The boiling point of a liquid is the temperature at which the vapor pressure of that liquid is equal to atmospheric pressure. The vapor pressure is the pressure exerted by the molecules of a volatile substance as they escape into the atmosphere. When the vapor pressure of a liquid equals atmospheric pressure, the liquid will boil.

However, not all liquids have the same vapor pressure at a given temperature. For example, water has a much higher vapor pressure than ice at room temperature. This means that water will boil at a lower temperature than ice.

So while boiling point is related to vapor pressure, it is not always equal to it.

## Conclusion

If you want to calculate the boiling point from the vapor pressure, you’ll need to know the atmospheric pressure. You can find this value in a weather report or online. Once you have that number, divide it by the vapor pressure.

The resulting number is the boiling point.

Joseph is an HVAC technician and a hobbyist blogger. He’s been working as an HVAC technician for almost 13 years, and he started blogging just a couple of years ago. Joseph loves to talk about HVAC devices, their uses, maintenance, installation, fixing, and different problems people face with their HVAC devices. He created Hvacbuster to share his knowledge and decade of experiences with people who don’t have any prior knowledge about these devices.