Answer is (b) , because a chemical change happened
Enthalpy of formation is calculated by subtracting the total enthalpy of formation of the reactants from those of the products. This is called the HESS' LAW.
ΔHrxn = ΔH(products) - ΔH(reactants)
Since the enthalpies are not listed in this item, from reliable sources, the obtained enthalpies of formation are written below.
ΔH(C2H5OH) = -276 kJ/mol
ΔH(O2) = 0 (because O2 is a pure substance)
ΔH(CO2) = -393.5 kJ/mol
ΔH(H2O) = -285.5 kJ/mol
Using the equation above,
ΔHrxn = (2)(-393.5 kJ/mol) + (3)(-285.5 kJ/mol) - (-276 kJ/mol)
ΔHrxn = -1367.5 kJ/mol
<em>Answer: -1367.5 kJ/mol</em>
Equilibrium chemical reaction between chair and boat forms is:
Kc =
![\frac{[Boat form]}{[Chair form]}](https://tex.z-dn.net/?f=%20%5Cfrac%7B%5BBoat%20form%5D%7D%7B%5BChair%20form%5D%7D%20)
Suppose the total number of molecules is x
Number of molecules of chair form is 6.42/100 x
Number of molecules of boat form is 93.58/100 x
Kc =

= 14.6