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(a) One method of producing neutrons for experimental use is bombardment of light nuclei with alpha particles. In the method used by James Chadwick in $1932,$ alpha particles emitted by polonium are incident on beryllium nuclei: $$ _{2} \mathrm{He}+_{4}^{9} \mathrm{Be} \rightarrow_{6}^{12} \mathrm{C}+_{0}^{1} \mathrm{n} $$ What is the $Q$ value of this reaction? (b) Neutrons are also often produced by small-particle accelerators. In one design, deuterons accelerated in a Van de Graaff generator bombard other deuterium nuclei and cause the reaction $$ _{1}^{2} \mathrm{H}+_{1}^{2} \mathrm{H} \rightarrow_{2}^{3} \mathrm{He}+_{0}^{1} \mathrm{n} $$ Calculate the Q value of the reaction. (c) Is the reaction in part (b) exothermic or endothermic?

          (a) One method of producing neutrons for experimental use is bombardment of light nuclei with alpha particles. In the method used by James Chadwick in $1932,$ alpha particles emitted by polonium are incident on beryllium nuclei:
$$ _{2} \mathrm{He}+_{4}^{9} \mathrm{Be} \rightarrow_{6}^{12} \mathrm{C}+_{0}^{1} \mathrm{n} $$ What is the $Q$ value of this reaction? (b) Neutrons are also often produced by small-particle accelerators. In one design, deuterons accelerated in a Van de Graaff generator bombard other deuterium nuclei and cause the reaction $$ _{1}^{2} \mathrm{H}+_{1}^{2} \mathrm{H} \rightarrow_{2}^{3} \mathrm{He}+_{0}^{1} \mathrm{n} $$ Calculate the Q value of the reaction. (c) Is the reaction in part (b) exothermic or endothermic?

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