Manipal Medical Manipal Medical Solved Paper-2011

  • question_answer
    A metal oxide has the formula\[{{A}_{2}}{{O}_{3}}\]. It can be reduced by hydrogen to give free metal and water. 0.1596 g of this metal oxide requires 6 mg of hydrogen for complete reduction. What is the atomic weight of metal?

    A)  \[52.3\]   

    B)  \[57.5\] 

    C)  \[55.8\]  

    D)  \[59.3\]

    Correct Answer: C

    Solution :

     \[\underset{0.1596\text{ }g}{\mathop{{{A}_{2}}{{O}_{3}}}}\,+\underset{0.006\text{ }g}{\mathop{3{{H}_{2}}}}\,\xrightarrow[{}]{{}}2A+3{{H}_{2}}O\] 0.006 g of\[{{H}_{2}}\]reduces 0.1596 g of\[{{A}_{2}}{{O}_{3}}\] 6 g of\[{{H}_{2}}\]will reduces \[=\frac{0.01596\times 6}{0.006}=159.6\,g\,{{A}_{2}}{{O}_{3}}\] Hence, molecular weight of\[{{A}_{2}}{{O}_{3}}=159.6\text{ }g\] Let molecular weight of \[A=x\] \[\therefore \] \[2x\times 3\times 16=159.6\] or    \[2x=159.6-48\] or    \[2x=111.6\] or     \[x=55.8\]


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