Uttarakhand PMT Uttarakhand PMT Solved Paper-2004

  • question_answer
    If the value of\[{{C}_{p}}\]for nitrogen gas is \[j{{K}^{-1}}mo{{l}^{-1}},\]then the value of\[\Delta H\]on heating 28 g of nitrogen gas from\[0{}^\circ C\]to\[100{}^\circ C\]at constant pressure will be:

    A)  1200 J      

    B)  1300 J

    C)  1400 J       

    D)  1500 J

    Correct Answer: C

    Solution :

     Given that: \[{{C}_{p}}=7\,J{{K}^{-1}}mo{{l}^{-1}}\] Weight of\[{{N}_{2}}\]gas = 28 gm \[{{T}_{1}}=0{}^\circ C=273+0=273\text{ }K\] \[{{T}_{2}}=100{}^\circ C=273+100=373\text{ }K\] Now, by using: Number of moles \[=\frac{Weight\text{ }of\text{ }{{N}_{2}}}{Molecular\text{ }weight\text{ }of\text{ }{{N}_{2}}}=\frac{28}{14}=2\] Now, by using \[\Delta H=n{{C}_{p}}({{T}_{2}}-{{T}_{1}})=2\times 7(373-273)\] \[=14\times 100=1400\text{ }Joule\]


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