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NEET Sample Paper NEET Sample Test Paper-66

  • question_answer
    25.3 g sodium carbonate, \[N{{a}_{2}}C{{O}_{3}}\] was dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of \[N{{a}^{+}}\] and carbonate ions are respectively: \[(Molar\,\,mass\,\,of\,\,N{{a}_{2}}C{{O}_{3}}\,=\,\,106\,\,g\,mo{{l}^{-1}})\]

    A) 0.9555 M and 1.910 M

    B) 1.910 M and 0.955 M

    C) 1.90 M and 1.090 M

    D) 0.477 M and 0.477 M

    Correct Answer: B

    Solution :

    \[{{M}_{N{{a}_{2}}C{{O}_{3}}}}\,=\,\,{{M}_{N{{a}^{+}}}}\times 2={{M}_{CO_{3}^{2-}}}\,and\,\,{{M}_{N{{a}_{2}}C{{O}_{3}}}}\]\[=\,\,\frac{25.3\times 1000}{106\times 250}\,=\,\,0.955\] \[\Rightarrow \,\,\,0.955\,\,\times \,\,2\,\,=\,\,1.91\text{ }M\] Thus is correct.


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