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KVPY Sample Paper KVPY Stream-SX Model Paper-23

  • question_answer
    Which of the following metal salts gives a red and opaque borax bead in the reducing flame (in cold)?

    A) Ni

    B) Fe   

    C) Cu       

    D) Mn

    Correct Answer: C

    Solution :

    \[N{{a}_{2}}{{B}_{4}}{{O}_{7}}\,\,\xrightarrow{\Delta }\,\,2NaB{{O}_{2}}+{{B}_{2}}{{O}_{3}}\]
    \[CuO+{{B}_{2}}{{O}_{3}}\,\,\xrightarrow{\Delta }\,\,Cu{{(B{{O}_{2}})}_{2}}\]
    \[2Cu\,{{(B{{O}_{2}})}_{2}}+4\,NaB{{O}_{2}}+2C\,\,\xrightarrow{\Delta }\](red and opaque)


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