Question

question 12 (1 point)
use the following information to answer the next question.
when graphite combines with hydrogen and gaseous
oxygen, one mole of ethyl alcohol is formed.
2c(graphite) + 3h₂(g) + ½o₂(g) -> c₂h₅oh δfh⁰ = -
2777.7 kj/mol
which of the following statements is true for the above reaction?
the above reaction is endothermic in nature.
in the above reaction, one mole of a compound is formed from its elements.
the reaction, which is exothermic in the forward direction, is exothermic in the
reverse direction also.
the δh is the heat of combustion of c₂h₅oh.
none of the above statements are true

Explanation:

• Endothermic vs Exothermic: Since $\Delta H=-2777.7\ \text{kJ/mol}$ (negative value), the reaction is exothermic, not endothermic. So the first option is wrong.
• Formation from elements: The reaction shows \(2C(\text{graphite}) + 3H_2(g)+\frac{1}{2}O_2(g)\to C_2H_5OH\). Graphite (\(C\)), \(H_2\) and \(O_2\) are elements, and one mole of \(C_2H_5OH\) (a compound) is formed. This matches the definition of heat of formation.
• Exothermic in reverse: If a reaction is exothermic (\(\Delta H<0\)) in the forward direction, it is endothermic (\(\Delta H > 0\)) in the reverse direction. So the third option is wrong.
• Heat of combustion: Heat of combustion is the heat change when one mole of a substance reacts with oxygen to form \(CO_2\) and \(H_2O\). Here, it is heat of formation (\(\Delta_fH\)) as it is formation from elements, not combustion. So the fourth option is wrong.

Answer:

In the above reaction, one mole of a compound is formed from its elements.