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NEET Sample Paper NEET Sample Test Paper-43

  • question_answer
    A vessel, fitted with a weightless, firiction less piston of 0.025 \[{{m}^{2}}\] area, contains excess cone. HCl. The piston moved 1 m outward when 0.075kg of iron fillings were added at 300 K. The solution left behind was found to contain Fe (II).The approximate purity of the iron sample is -

    A) 50%                 

    B) 75%

    C) 90%                             

    D) 40%

    Correct Answer: B

    Solution :

    \[Fe+2HC1\text{ }\left( excess \right)\xrightarrow{{}}FeC{{1}_{2}}+{{H}_{2}}\] 75 g Fe Vol. of \[{{H}_{2}}=area\times displacement\] \[=0.025\times 1\text{ }{{m}^{3}}=0.025\times {{10}^{3}}\text{ }lit=25\text{ }lit\] If Fe is x% pure             \[E{{q}_{Fe}}=E{{q}_{{{H}_{2}}}}\] at 300 K; PV = nRT \[1\times 25=n\times 0.08\times 300\] \[n=1.04\,\,mol={{2.08}_{g}}{{H}_{2}}\] \[E{{q}_{Fe}}=E{{q}_{{{H}_{2}}}},\] \[\frac{0.75x}{\left( \frac{56}{2} \right)}=\frac{2.08}{1}\] x = 75% approx.


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