In calculating the change in enthalpy in a certain reaction, it is important to remember that it is the sum of the enthapy of formation for the substances involved in the reaction.
<span>CaO(s)+2HCl(aq)→CaCl2(aq)+H2O(l) ΔH= –186kJ
</span>Ca(OH)2(aq) → CaO(s)+H2O(l)<span> ΔH= 65.1 kJ
</span>Ca(OH)2(aq) + 2HCl(aq) → CaCl2(aq) + 2H2O(l) ΔH= -120.9 kJ
The answer is B, Neutron star
The reaction for burning of charcoal or complete combustion is as follows:

From the above balanced reaction, 1 mole of carbon releases 1 mole of
gas.
Converting mass of charcoal into moles as follows:

Molar mass of pure carbon is 12 g/mol thus,

The same moles of
is released. Converting these moles into mass as follows:
m=n×M
Molar mass of
is 44 g/mol thus,

Converting mass into kg,

Thus, total mass of gas released is 5.5 kg.