# Enthelpy of a reaction question

• wintermute++
In summary, the conversation discusses the difference between enthalpy and internal energy in a gas-phase reaction carried out in a constant-volume container at constant temperature. It is concluded that both delta U and delta H are equal to q, but the constant temperature condition raises questions about how heat can change without affecting the temperature inside the vessel.
wintermute++
Suppose that the gas-phase reaction 2NO + O2 --- 2NO2 were carried out in a constant-volume container at constant temperature. Would the measured heat change represent a change in enthalpy or a change in internal energy? If there is a difference, which quantity is larger for this reaction? Explain.delta U = q + w
delta H = delta U + P(delta V)I've been able to reduce the two equations so that delta U = q given a constant-pressure and volume container. Of course, delta H is also equal to q. So from that, the internal energy and enthalpy change would be equal. Or so I would assume.

What is throwing me off is the constant-temperature. If the value of q is changing but the temperature is constant and so is the ability to work... I just don't understand how the temperature cannot change given the other conditions if a change in heat occurs.

Any help?

Heat is transferred outside, so that temperature inside of the vessel doesn't change.

## What is the definition of Enthalpy of a reaction?

The Enthalpy of a reaction, also known as the heat of reaction, is the amount of heat released or absorbed during a chemical reaction. It is a measure of the energy change that occurs as a result of the reaction.

## How is the Enthalpy of a reaction calculated?

The Enthalpy of a reaction is calculated by subtracting the sum of the enthalpies of the reactants from the sum of the enthalpies of the products. This can be represented by the equation: ΔH = ΣH(products) - ΣH(reactants).

## What factors can affect the Enthalpy of a reaction?

The Enthalpy of a reaction can be affected by various factors, including the temperature, pressure, and concentration of the reactants and products. Catalysts can also affect the Enthalpy of a reaction by lowering the activation energy and increasing the rate of the reaction.

## Why is Enthalpy of a reaction important in chemistry?

Enthalpy of a reaction is an important concept in chemistry because it helps us understand the energy changes that occur during a chemical reaction. It also allows us to predict the direction of a reaction, whether it will release or absorb heat, and how much energy will be involved.

## What is the difference between Enthalpy of a reaction and Enthalpy of formation?

Enthalpy of a reaction refers to the energy change that occurs during a specific chemical reaction, while Enthalpy of formation is the energy change that occurs when one mole of a substance is formed from its constituent elements in their standard states. Enthalpy of formation is often used to determine the Enthalpy of a reaction.

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