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When 1g of water at 100 0 C is converted iinintintointo steam aatat 100 0 C,it occupies a volume of 1671cc at normal atmospheric pressure. Find the increase in internal energy of the molecules of steam

When 1g of water at 1000C is converted iinintintointo steam aatat 1000C,it occupies a volume of 1671cc at normal atmospheric pressure. Find the increase in internal energy of the molecules of steam

Grade:11

1 Answers

Arun
25758 Points
3 years ago

here we shall use the first law of thermodynamics

ΔQ = ΔU + ΔW

so, change in internal energy will be

ΔU = ΔQ - ΔW 

here,

ΔQ = mL =1g x 540Cal/g = 540 Cal

ΔU  = change in internal energy (to be calculated)

ΔW = change in work done

so,

ΔW = pΔV 

where

ΔV = 1671cm3 - 1cm3 = 1670cm3 = 1670 x 10-6 m3

p = hρg = 0.76 x 13600 x 9.8 ~ 101293 N/m2

so,

ΔW = 101293 x 1670x10-6 = 169.16J

or

ΔW = 169.16 / 4.2 = 40.3 Cal

thus, we have

 ΔU = 540 Cal - 40.3 Cal

so,

 ΔU = 499.7 Cal = 2098.74 J

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