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VMMC VMMC Medical Solved Paper-2015

  • question_answer
    What will be the mass of water vapour per cubic metre of air at temperature 300 K and relative humidity 25%? The saturation vapour pressure at 300 K is 3.6 kPa and gas constant is \[R=8.3J{{K}^{-1}}\]

    A) 13g                                        

    B) 26g

    C) 6.5 g                                      

    D) None of these

    Correct Answer: C

    Solution :

    At temperature 300 K, the saturation vapour  pressure is 3.6kPa for unit volume, i.e. 1m3       \[pV=nRT=\frac{m}{M}RT\]where, m = mass of vapour and M = molar weight of water                   Thus,\[m=\frac{MpV}{RT}=\frac{18\times 3.3\times {{10}^{3}}\times 1}{8.3\times 300}\]\[\simeq 26g\] As, relative humidity is 25%                    Therefore, the amount of mercury present in unit volume is\[26\times 0.25=6.5\text{ }g\]                  


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