Which of the following are applicable for a thermochemical equation ? It tells `:`

Options

A. It tells about physical state of reactants and products
B. It tells whether the reaction is spontaneous
C. It tells whether the reaction is exothermic or endothermic
D. It tells about the allotropic form (if any) of the reactants

Answer

To solve the question regarding the applicability of a thermochemical equation, we will analyze the characteristics and implications of such equations step by step.

### Step 1: Understanding Thermochemical Equations
A thermochemical equation is a balanced chemical equation that includes the enthalpy change (ΔH) associated with the reaction. It provides information about the states of the reactants and products (solid, liquid, gas) and the heat absorbed or released during the reaction.

**Hint:** Remember that a thermochemical equation must include the physical states of all reactants and products.

### Step 2: Identifying Key Features
1. **States of Reactants and Products:** A thermochemical equation specifies whether the substances involved are in solid, liquid, or gaseous states.
2. **Enthalpy Change:** It indicates whether the reaction is exothermic (ΔH < 0) or endothermic (ΔH > 0).
3. **Allotropic Forms:** If any reactants or products exist in different allotropes, the thermochemical equation will specify which allotrope is involved.

**Hint:** Focus on the information that can be derived directly from the enthalpy change and the states of matter.

### Step 3: Evaluating the Statements
Now, we will evaluate the statements provided in the question based on the characteristics identified.

- **Statement A:** "It tells whether the reaction is spontaneous."
- This statement is **incorrect**. Spontaneity is determined by Gibbs free energy (ΔG), not just the enthalpy change (ΔH).

- **Statement B:** "It tells whether the reaction is exothermic or endothermic."
- This statement is **correct**. The sign of ΔH indicates whether the reaction releases heat (exothermic) or absorbs heat (endothermic).

- **Statement C:** "It tells the states of reactants and products."
- This statement is **correct**. A thermochemical equation explicitly includes the physical states of all substances involved.

- **Statement D:** "It tells about the allotropic form if any of the reactants have."
- This statement is **correct**. The equation can specify the allotrope of a reactant if applicable.

### Conclusion
Based on the evaluation, the applicable statements for a thermochemical equation are:
- Statement B (exothermic or endothermic)
- Statement C (states of reactants and products)
- Statement D (allotropic forms)

Thus, the correct answers are **B, C, and D**.

**Final Answer:** The applicable statements for a thermochemical equation are B, C, and D.