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Question
In Joly's differential steam calorimeter, 3 g of an ideal gas is contained in a rigid closed sphere at 20°C. The sphere is heated by steam at 100°C and it is found that an extra 0.095 g of steam has condensed into water as the temperature of the gas becomes constant. Calculate the specific heat capacity of the gas in J g−1 K−1. The latent heat of vaporisation of water = 540 cal g−1
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Solution
For Joly's differential steam calorimeter,
`"C"_"v" = ("m"_2"L")/"m"_1 (theta _ 2 - theta_1),`
where
m2 = mass of steam condensed
m2 = 0.095 g
Latent heat of vapourization, L = 540 cal/g = 540 × 4.2 J/g
m1 = mass of gas present
m1 = 3 g
Initial temperature, θ1 = 20°C
Final temperature, θ2 = 100°C
`=> "C"_"v" = (0.095 xx 540 xx 4.2)/(3 xx (100-20)`
= 0.89 = 0.9 J/ g-K
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