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Vapor Pressure and Boiling Point

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  A liquid boils when its vapor pressure equals the external pressure 
acting on the surface of the liquid. At this point bubbles of vapor are 
able to form within the interior of the liquid. The temperature of 
boiling increases with increasing external pressure. The boiling point 
of a liquid at 1 atm pressure is called its normal boiling point. From 
Figure 11.22 we see that the normal boiling point of water is 100°C.

The boiling point is important to many processes that involve heating 
liquids, including cooking. The time required to cook food depends on 
the temperature. As long as water is present, the maximum temperature of 
the cooking food is the boiling point of water. Pressure cookers work by 
allowing steam to escape only when it exceeds a predetermined pressure; 
the pressure above the water can therefore increase above atmospheric 
pressure. The higher pressure causes water to boil at a higher 
temperature, thereby allowing the food to get hotter and to cook more 
rapidly. The effect of pressure on boiling point also explains why it 
takes longer to cook food at higher elevations than at sea level. The 
atmospheric pressure is lower at higher altitudes, so water boils at a 
lower temperature.




  SAMPLE EXERCISE 11.5

Use Figure 11.22 to estimate the boiling point of diethyl ether under an 
external pressure of 600 torr.

(figure is here 
http://wps.prenhall.com/wps/media/objects/3311/3391416/blb1105.html  )

SOLUTION The boiling point is the temperature at which the vapor 
pressure is equal to the external pressure. From Figure 11.22 we see 
that the boiling point at 600 torr is about 27°C, which is close to room 
temperature. We can make a flask of diethyl ether boil at room 
temperature by using a vacuum pump to lower the pressure above the 
liquid to about 600 torr.

PRACTICE EXERCISE

At what external pressure will ethanol have a boiling point of 60°C? 
Answer: about 350 torr

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Vapor Pressure and Boiling Point Serg io <invalid@invalid.com> - 2017-03-27 15:42 -0500
  Re: Vapor Pressure and Boiling Point noTthaTguY <abu.kuanysh05@gmail.com> - 2017-03-27 14:48 -0700
  Re: Vapor Pressure and Boiling Point James McGinn <jimmcginn9@gmail.com> - 2017-03-27 15:28 -0700
  Re: Vapor Pressure and Boiling Point James McGinn <jimmcginn9@gmail.com> - 2017-03-28 08:13 -0700
    Re: Vapor Pressure and Boiling Point noTthaTguY <abu.kuanysh05@gmail.com> - 2017-03-28 09:54 -0700
  Re: Vapor Pressure and Boiling Point "reber G=emc^2" <herbertglazier0@gmail.com> - 2017-04-01 14:55 -0700
    Re: Vapor Pressure and Boiling Point jimp@specsol.spam.sux.com - 2017-04-01 22:18 +0000
      Re: Vapor Pressure and Boiling Point pnalsing@gmail.com - 2017-04-02 19:44 -0700
        Re: Vapor Pressure and Boiling Point jimp@specsol.spam.sux.com - 2017-04-03 05:34 +0000
          Re: Vapor Pressure and Boiling Point Serg io <invalid@invalid.com> - 2017-04-03 16:24 -0500
            Re: Vapor Pressure and Boiling Point Serg io <invalid@invalid.com> - 2017-04-03 16:25 -0500
            Re: Vapor Pressure and Boiling Point jimp@specsol.spam.sux.com - 2017-04-03 21:40 +0000
              Re: Vapor Pressure and Boiling Point "reber G=emc^2" <herbertglazier0@gmail.com> - 2017-04-04 13:36 -0700
                Re: Vapor Pressure and Boiling Point Double-A <double-a3@hush.com> - 2017-04-04 14:11 -0700
                Re: Vapor Pressure and Boiling Point jimp@specsol.spam.sux.com - 2017-04-04 21:24 +0000
                Re: Vapor Pressure and Boiling Point benj <benj@nobody.net> - 2017-04-04 19:59 -0400
                Re: Vapor Pressure and Boiling Point jimp@specsol.spam.sux.com - 2017-04-05 00:14 +0000
                Re: Vapor Pressure and Boiling Point jimp@specsol.spam.sux.com - 2017-04-04 21:14 +0000
                Re: Vapor Pressure and Boiling Point "hanson" <hanson@quick.net> - 2017-04-04 14:41 -0700
      Re: Vapor Pressure and Boiling Point "reber G=emc^2" <herbertglazier0@gmail.com> - 2017-04-04 13:37 -0700
        Re: Vapor Pressure and Boiling Point "hanson" <hanson@quick.net> - 2017-04-04 14:42 -0700
    Re: Vapor Pressure and Boiling Point "hanson" <hanson@quick.net> - 2017-04-01 18:00 -0700
    Re: Vapor Pressure and Boiling Point Double-A <double-a3@hush.com> - 2017-04-02 15:03 -0700
      Re: Vapor Pressure and Boiling Point noTthaTguY <abu.kuanysh05@gmail.com> - 2017-04-02 18:22 -0700

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