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Q.
In carbon cycle of nuclear fusion, $C$ acts as
UP CPMTUP CPMT 2007
Solution:
Carbon cycle : $A$ cycle of nuclear reactions resulting in the formation of one helium nucleus from four hydrogen nuclei, with the emission of gamma rays $(\gamma}$, positrons $(e^{+}$, neutrinos $\left(\upsilon\right)$ and a large amount o f energy. The set o f reactions are as follows
$^{12}_{6}C+^{1}_{1}H \to^{13}_{7}N +\gamma+1.93 MeV \ldots\left(i\right)$
$^{13}_{7}N\to^{13}_{6}C+c^{+}+\upsilon+1.20 MeV \ldots\left(ii\right)$
$^{13}_{6}C+^{1}_{1}H \to^{14}_{7}N+\gamma+7.6\,MeV \ldots\left(iii\right)$
$^{14}_{7}N+^{1}_{1}H \to^{15}_{8}O+\gamma+7.39\,MeV \ldots\left(iv\right)$
$^{15}_{8}O \to^{15}_{7}N+e^{+}+\upsilon+1.71\,MeV \ldots\left(v\right)$
$^{15}_{7}N+^{1}_{1}H \to^{12}_{6}C+^{-4}_{2}He+4.99\,MeV \ldots\left(vi\right)$
The overall reaction can be written as
$4^{1}_{1}H+^{12}_{6}C \to ^{4}_{2}He+^{12}_{6}C+2e^{+}+2\upsilon+3\gamma+24.8\,MeV$
The carbon is reformHed at the end of the cycle and therefore acts as a catalyst. The carbon cycle occurs in stars hotter than the sun