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Stoichiometry - Engineering

Q1:

The heat change for the reaction, C(s) + 2S(s) → CS2(l), is 104.2 kJ. It represents the heat of

A formation

B solution

C combustion

D fusion

ANS:A - formation

The heat change for a chemical reaction can represent different types of energy changes depending on the context of the reaction. Let's analyze the options provided:

  1. Heat of formation: This refers to the heat change that occurs when one mole of a compound is formed from its constituent elements in their standard states. In this reaction, CS2(l) is formed from C(s) and S(s). However, the given reaction does not involve the formation of elements from their standard states, so it's unlikely to be the heat of formation.
  2. Heat of solution: This refers to the heat change that occurs when a solute is dissolved in a solvent to form a solution. This reaction does not involve the dissolution of a solute in a solvent, so it's unlikely to be the heat of solution.
  3. Heat of combustion: This refers to the heat change that occurs when one mole of a substance undergoes complete combustion with oxygen. In this reaction, no oxygen is involved, so it's unlikely to be the heat of combustion.
  4. Heat of fusion: This refers to the heat change that occurs when one mole of a substance changes from a solid to a liquid state at its melting point. In the given reaction, CS2(l) is formed from C(s) and S(s), indicating a change from solid to liquid state for CS2. Therefore, it's likely to be the heat of fusion.
So, based on the provided options, the heat change for the reaction C(s)+2S(s)→CS2(l)C(s)+2S(s)→CS2​(l) is likely to represent the heat of fusion.