Answer
4.11 eV/atom
Work Step by Step
According to the question, the reaction releases $3.3 \times 10^{7}$ J energy when 1kg of atomic carbon is used in the reaction.
We can find the number of carbon atoms present in 1 kg of atomic carbon.
The mass of a carbon atom is $(12.0 \mathrm{u})\left(1.661 \times 10^{-27} \mathrm{kg} / \mathrm{u}\right)=1.99 \times 10^{-26} \mathrm{kg}$
$\therefore$ Number of carbon atoms in $1.00 \mathrm{kg}$ of carbon is
$$
(1.00 \mathrm{kg}) /\left(1.99 \times 10^{-26} \mathrm{kg}\right)=5.02 \times 10^{25} atoms
$$
The heat of combustion per atom is
$$
\left(3.3 \times 10^{7} \mathrm{J} / \mathrm{kg}\right) /\left(5.02 \times 10^{25} \mathrm{atom} / \mathrm{kg}\right)=6.58 \times 10^{-19} \mathrm{J} / \mathrm{atom}
$$
This is 4.11 eV/atom.
