5. Why is a burn from 373K steam more severe than a burn from 373K water? 6. Cal

Question

5. Why is a burn from 373K steam more severe than a burn from 373K water?

6. Calculate the energy (heat) required to transform 18.02 g ice at 253K into steam at 393K.

7. Why is it that boiling water at 1 atm pressure MUST be at 100C?

8.What is the vapor pressure of boiling water (in atm) if atmospheric pressure is 1 atm?

9. The vapor pressure of benzene at 20C is 0.099 atm. The vapor pressure of toluene at 20C is 0.029 atm. Which chemical will evaporate faster? Will either chemical boil at 20C at sea level? List TWO ways to get benzene to boil.

Explanation / Answer

5) Because steam will have letent heat, which will cause severe effect that water, even though both are at same temperature. The same temperatue is due to same kinetic energy.

6) we know that the latent heat of water for fusion = 333.55 j/g, vapourisation = 2270 j/g

    Heat required to convert 18.02g ice at 253 K to water at same temperature Q1 = 18.02g x 333.55 j/g = 6010.571j

    Heat required to convert liquid water from 253K to 393K Q2 = mxCxDelta T= 18.02 x 4.18 x 140 K = 10545.304 j

    Heat required to convert water at 393K to steam Q3 = 18.02g x 2270 j/g = 40905.4j

    Total Heat = Q1+Q2+Q3 = 57.4612 KJ

7) In other way you can understand correctly. Boiling point is that where the vapour pressure of the water is equals to atmospheric pressure. so exactly at 100 C, the vapour pressure of water will be equal to atmospheric pressure, i.e 1 atm.

8) That is 1 atm or 760 mm.Hg

9) As the benzene was had high vapor pressure, it will be evaporate faster.

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