"The change of enthalpy of a chemical reaction is the same whether the reaction takes place in one step or in several steps". This law was presented by:

Options

A. Le Chatelier's law
B. vant's Hoff's law
C. first law of thermodynamics
D. Hess's law.

Answer

To solve the question, "The change of enthalpy of a chemical reaction is the same whether the reaction takes place in one step or in several steps. This law was presented by:", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Statement**: The statement refers to a principle regarding the change of enthalpy in chemical reactions, indicating that the total enthalpy change is independent of the pathway taken (one step vs. multiple steps).

2. **Identify the Law**: The law that describes this principle is known as Hess's Law. It states that the total enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps of the reaction.

3. **Recall the Definition of Hess's Law**: Hess's Law, also known as the Law of Constant Heat Summation, asserts that the enthalpy change of a chemical reaction is the same regardless of whether the reaction occurs in one step or multiple steps.

4. **Consider Other Laws**: To ensure that Hess's Law is the correct answer, briefly review other related laws:
- **Le Chatelier's Principle**: Deals with the response of a system at equilibrium to changes in concentration, temperature, or pressure.
- **Van 't Hoff's Law**: Relates to the effect of temperature on the rate of chemical reactions.
- **First Law of Thermodynamics**: States that energy cannot be created or destroyed, only transformed.

5. **Select the Correct Answer**: Based on the understanding and definitions, the correct answer to the question is Hess's Law.

### Final Answer:
The law presented by Hess, which states that the change of enthalpy of a chemical reaction is the same whether the reaction takes place in one step or in several steps, is known as **Hess's Law**.

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