12th Class Chemistry Nuclear Chemistry / नाभिकीय रसायन Question Bank Critical Thinking Nuclear chemistry

  • question_answer
    Consider an a-particle just in contact with a \[_{92}{{U}^{238}}\]nucleus. Calculate the coulombic repulsion energy (i.e. the height of the coulombic barrier between \[{{U}_{238}}\] and alpha particle) assuming that the distance between them is equal to the sum of their radii                                                      [UPSEAT 2001]

    A)            23.8517×\[{{10}^{4}}eV\]

    B)            \[26.147738\times \text{1}{{\text{0}}^{\text{4}}}eV\]

    C)            \[\text{25}\text{.3522}\times {{10}^{4}}eV\]

    D)            \[20.2254\times {{10}^{4}}eV\]

    Correct Answer: B

    Solution :

           \[{{r}_{\text{nucleus}}}=\text{1}\text{.3}\times \text{1}{{\text{0}}^{\text{-13}}}\times {{(A)}^{1/3}},\] where A is mass number                    \[{{r}_{{{U}^{238}}}}=1.3\times {{10}^{-13}}\times {{(238)}^{1/3}}=8.06\times {{10}^{-13}}cm.\]                    \[{{r}_{H{{e}^{4}}}}=1.3\times {{10}^{-13}}\times {{(4)}^{1/3}}=2.06\times {{10}^{-13}}cm.\]                    \Total distance in between uranium and \[\alpha \] nuclei                              = 8. 06× \[{{10}^{-13}}\] + 2.06 × \[{{10}^{-13}}\] = 10.12 × \[{{10}^{-13}}\]cm            Now repulsion energy = \[\frac{{{Q}_{1}}{{Q}_{2}}}{r}=\frac{92\times 4.8\times {{10}^{-10}}\times 2\times 4.8\times {{10}^{-10}}}{10.12\times {{10}^{-13}}}erg\]                    \[=418.9\times {{10}^{-7}}erg\]= \[418.9\times {{10}^{-7}}\times 6.242\times {{10}^{11}}eV\]                    = \[26.147738\times {{10}^{4}}eV.\]


You need to login to perform this action.
You will be redirected in 3 sec spinner