NEET AIPMT SOLVED PAPER SCREENING 2006

  • question_answer
                    Consider the reaction                 \[{{N}_{2}}(g)+3{{H}_{2}}(g)\xrightarrow{{}}2N{{H}_{3}}(g)\]                 The equality relationship between \[\frac{d[N{{H}_{3}}]}{dt}\] and \[-\frac{d[{{H}_{2}}]}{dt}\] is:                                                            

    A)                  \[\frac{d\,[N{{H}_{3}}]}{dt}=-\frac{1}{3}\,\frac{d\,[{{H}_{2}}]}{dt}\]                                       

    B)                  \[+\frac{d\,[N{{H}_{3}}]}{dt}=-\frac{2}{3}\,\frac{d\,[{{H}_{2}}]}{dt}\]    

    C)                  \[+\frac{d\,[N{{H}_{3}}]}{dt}=-\frac{3}{2}\,\frac{d\,[{{H}_{2}}]}{dt}\]                                    

    D)                  \[\frac{d\,[N{{H}_{3}}]}{dt}=-\,\frac{d\,[{{H}_{2}}]}{dt}\]

    Correct Answer: B

    Solution :

                    For the reaction,                 \[{{N}_{2}}(g)+3{{H}_{2}}(g)\xrightarrow[{}]{{}}2N{{H}_{3}}(g)\]                 The rate of reaction w.r.t. \[{{N}_{2}}=-\frac{d\,[{{N}_{2}}]}{dt}\]                 The rate of reaction w.r.t \[{{H}_{2}}=-\frac{1}{3}\,\frac{d\,[{{H}_{2}}]}{dt}\]                 The rate of reaction w.r.t \[N{{H}_{3}}=+\frac{1}{2}\,\frac{d\,[N{{H}_{3}}]}{dt}\]                 Hence, at a fixed time                 \[-\frac{d[{{N}_{2}}]}{dt}=-\frac{1}{3}\,\frac{d\,[{{H}_{2}}]}{dt}\]                                                 \[=+\frac{1}{2}\,\frac{d\,[N{{H}_{3}}]}{dt}\]                         \[or+\frac{d\,[N{{H}_{3}}]}{dt}=-\frac{2}{3}\,\frac{d\,[{{H}_{2}}]}{dt}\]                         \[or-\frac{2d\,[{{N}_{2}}]}{dt}\]


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