# Solving a Thermodynamics Problem: Finding ΔHf for OH(g) in H2O2 (g) Reaction

• Dell
In summary, To find the enthalpy of formation for OH(g) in this thermodynamics problem, you will need to use the enthalpy of dissolution (ΔH(diss)) equation, which is equal to 213KJ/mol. Remember that ΔH(diss) is equal to the enthalpy of formation of products minus the enthalpy of formation of reactants. This means that you will need to find the enthalpy of formation of H2O2, which can be found in a table, and then solve for ΔH(OH). Some people have simplified this problem by saying that ΔH(diss) is equal to twice the enthalpy of formation of OH, but this may not always

#### Dell

How do i solve this chem, thermodynamics problem?
find ΔHf for OH(g) if

H2O2 (g)--> 2OH(g)

ΔH(diss)=213KJ/mol

what is ΔH(diss)?? what is 'diss'

someone told me The ΔH(diss)=213KJ/mol is equal to twice the ΔHf of OH. but i doont know how they got to this, also it seems a bit too simple for a qestion if all i need to do is divide by 2,
so how would i solve this?

Your $$\Delta H(diss)$$ is your enthalpy of reaction. Remember that the enthalpy of reaction equals: Enthalpy of formation of products - Enthalpy of formation of reactants. Replace your data (you will need to look for H2O2 enthalpy of formation on a table) there and solve for $$\Delta H(OH)$$.

To solve this thermodynamics problem, we first need to understand the notation and terms being used. ΔHf stands for the standard enthalpy of formation, which is the change in enthalpy when one mole of a substance is formed from its elements in their standard states. In this case, we are trying to find the ΔHf for OH(g), which is the enthalpy change when one mole of gaseous OH is formed from its elements in their standard states.

The reaction given is H2O2(g) → 2OH(g). This means that one mole of H2O2 gas is reacting to form two moles of OH gas. ΔH(diss) refers to the enthalpy change for this reaction, which is given as 213 kJ/mol. This is the heat released or absorbed during the reaction.

To solve for ΔHf for OH(g), we can use the following equation:

ΔH(diss) = 2ΔHf(OH) - ΔHf(H2O2)

Substituting the given values, we get:

213 kJ/mol = 2ΔHf(OH) - ΔHf(H2O2)

Rearranging the equation, we get:

ΔHf(OH) = (213 kJ/mol + ΔHf(H2O2)) / 2

To solve further, we need to know the value of ΔHf(H2O2). This can be found in thermodynamic tables or can be calculated using the same equation, with the known values for other substances involved in the formation of H2O2. Once we have the value for ΔHf(H2O2), we can substitute it into the equation and solve for ΔHf(OH).

In summary, to solve this thermodynamics problem, we need to use the given reaction and enthalpy change, understand the notation and terms used, and use the appropriate equations to calculate the ΔHf for OH(g). It may seem simple to divide the given value by 2, but it is important to understand the underlying concepts and equations to arrive at the correct answer.

## 1. What is thermodynamics and why is it important?

Thermodynamics is the study of energy and its transformation in a system. It is important because it helps us understand and predict how energy moves and changes in different systems, which is crucial for many fields of science and engineering.

## 2. What are the laws of thermodynamics?

The first law states that energy cannot be created or destroyed, only transferred or converted from one form to another. The second law states that the total entropy of a closed system will always increase over time. The third law states that the entropy of a perfect crystal at absolute zero temperature is zero.

## 3. How do you solve a thermodynamics problem?

To solve a thermodynamics problem, you need to first define the system and its boundaries, then apply the laws of thermodynamics and other relevant principles to analyze the energy transfers and transformations within the system. This often involves using mathematical equations and calculations.

## 4. What are some common applications of thermodynamics?

Thermodynamics has many applications in various fields, such as engineering (e.g. designing engines and power plants), chemistry (e.g. studying chemical reactions), and meteorology (e.g. understanding weather patterns). It is also crucial in understanding biological processes and ecosystems.

## 5. What are some challenges in solving thermodynamics problems?

One of the main challenges in solving thermodynamics problems is the complexity and non-linearity of many systems, which can make it difficult to accurately model and predict energy transfers and transformations. Additionally, some processes may be irreversible, making it challenging to apply the laws of thermodynamics precisely.