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NEET Chemistry Thermodynamics / रासायनिक उष्मागतिकी Question Bank Self Evaluation Test - Thermodynamics

  • question_answer
    Boron can undergo the following reactions with the given enthalpy changes: \[2B\left( s \right)+\frac{3}{2}{{O}_{2}}\left( g \right)\xrightarrow{{}}{{B}_{2}}{{O}_{3}}\left( s \right);\text{ }\Delta H=-1260\text{ }kJ\]\[2B(s)+3{{H}_{2}}(g)\xrightarrow{{}}{{B}_{2}}{{H}_{6}}(g);\Delta H=30kJ\] Assume no other reactions are occurring. If in a container (operating at constant pressure) which is isolated from the surrounding, mixture of \[{{H}_{2}}\](gas) and \[{{O}_{2}}\] (gas) are passed over excess of B(s), then calculate the molar ratio \[({{O}_{2}}:H)\] so that temperature of the container do not change :

    A) 15 : 3               

    B) 42 : 1

    C) 1 : 42               

    D) 1 : 84

    Correct Answer: D

    Solution :

    [d] No. of moles of \[{{O}_{2}}\] required to supplied 30 kJ heat to second reaction \[=\frac{30}{1260}\times \frac{3}{2}=\frac{1}{28}\] \[{{n}_{{{O}_{2}}}}:{{n}_{{{H}_{2}}}}=\frac{1}{28}:\,or\,\,1:84\]


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