JEE Main & Advanced Sample Paper JEE Main Sample Paper-47

  • question_answer
    2.4 g of a sample of metallic magnesium (atomic weight = 24) displaces, by reactions with dilute \[{{H}_{2}}S{{O}_{4}}\], 2 L of hydrogen gas measured at STP. The percentage purity of the sample of metal is

    A)  83.9                           

    B)  93.8              

    C)  98.3                           

    D)  89.3

    Correct Answer: D

    Solution :

     \[Mg+{{H}_{2}}S{{O}_{4}}\xrightarrow{\,}\,MgS{{O}_{4}}+{{H}_{2}}\uparrow \] 1 mol                           1 mol = 24 g                         = 22.4 L 24 g of Mg (pure) \[\equiv \,22.4\,L\,of\,{{H}_{2(g)}}\] at STP at STP \[\therefore \] 2.4 g (pure) = 2.24 L of \[{{H}_{2}}\] at STP \[\therefore \] Percentage purity \[=\frac{2.00}{2.24}\times 100=89.3%\]


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