boiling point of water increase to 374 degree if pressurised. Is it true & if yes, WHY?

Answer 1

We know that water boils at 100 °C (212 °F) at atmospheric pressure. The steam produced is at the same temperature and pressure and is called 'Saturated' steam.

Having worked on steam turbines and the boilers used to produce the steam, the pressure of the water (and steam) was held at 600 psi (about 41.5 bar).

At this pressure the water and saturated steam temperature was 486 °F. (252 °C).

The operation of a steam turbine requires high pressure, Superheated steam and, in the above case, the steam was heated further (superheated) to 775 °F (413 °C).

To simplify:
At higher pressure, the molecules of water have to 'struggle' harder to leave the water as steam. The increase in heat energy causes the molecular motion to increase to a point where the molecules can escape.

Answer 2

The temperature of boiling water depends on the pressure of the surrounding atmosphere. That's true.

It's actually a heat transfer question and has to do with equilibrium states. Start at sea level and 1 gallon of pure water at ambient temperature of 68 degrees. Neglect evaporation at this point.

How do we know that the water is boiling? What do we observe that tells us it's "boiling"? Answer: presence of vapor, observation of bubbles, turbulence of the surface.

How do we raise the temperature to where the boiling symptoms can be observed in a reasonable period? Answer: typically a heat source is placed IN the water or bears against the water container that can transfer heat. Unless we want to wait a very long time, we use a huge quantity of heat (between 9000-40000 BTUh) to cause the temperature to rise.

So. We have a considerable amount of heat INPUT. As we approach vapor production, the water temperature rises. There is some heat loss due to radiation and convection along the way. Once the water is "boiling" by producing water vapor or steam, the temperature stabilizes because the amount of heat OUTPUT as vapor or steam matches the heat input. It cannot get any hotter AT THAT PRESSURE.

Now constrain that quantity of water in a pressure vessel with a pressure release valve. Heat it as before to the "boiling" point. Since the water vapor cannot escape to remove heat from the liquid, the confined water vapor becomes steam and increases the pressure in the vessel. Since more heat is now retained in the liquid, its temperature must rise until the pressure relief valve opens. A new equilibrium point is reached at the higher pressure and temperature. If the relief valve is large enough to let out enough steam to dump the excess heat, we will simply waste input heat if we don't reduce the heat input. If the relief valve is too small, the pressure vessel will explode.

This is explained by the pressure-temperature-volume relationships, which I am certain is covered in your thermodynamics textbook.

Answer 3

Yes, putting water under pressure will increase its boiling temperature. This is the reason you need to cook food longer at higher elevations as water boils at a cooler temperature. This relationship is not a simple relationship and the boiling point is not directly proportional to the pressure. There are charts and tables in most thermodynamics textbooks which show the different phases of water and under what conditions each phase occurs. For the person who cited the ideal gas law, you are thinking about a totally different phenomena, the thermal expansion of an ideal gas (like Helium gas) not the boiling point of an incompressible fluid (water).

Answer 4

When external pressure is applied, the kinetic energy of the molecules in the vapor phase increases and the number of collisions also increase. Hence more molecules from the liquid are driven back into the liquid thus increasing the boiling point. More energy needs to be supplied to raise the kinetic energy of the molecules to stay in the vapor phase above the liquid.

So, yes, it is true. You got the why above.

Answer 5

yes it is true.. cause when the pressure is raised the distance between molecules can not increase by heating so the water boiling point will increase when the pressure is increase

Answer 6

Yes, the vapour pressure of water increases.

Answer 7

It is true If if u apply preasure to 221.29 bar, u get 374,15 degrees.

You need tables to get this data, tables from measurements.

For boiling water there is no easy relation between preasure vs
temperature. You need a Molliere-diagram or tables.

Answer 8

yes it is true.

theres a simple equation where boiling point is directly propertional to the pressure.

Answer 9

PV = NRT

If you increase pressure (P) then temperature (T) will increase

So the statement is false. It will do the opposite - boiling point will decrease if pressurized