Consider the reaction 2 H2O(g) ⟶ 2 H2(g)+O2(g) Δ H=483.6 kJ / mol If 2.0 moles of H2

Name: Problem 27, Chapter 6: Chemistry
Uploaded: 2020-06-26T01:06:47-08:00
Duration: 2 min 19 s
Channel: Nicole Bylsma
Description: Consider the reaction 2 H2O(g) ⟶ 2 H2(g)+O2(g) Δ H=483.6 kJ / mol If 2.0 moles of H2 O(g) are converted to H2(g) and O2(g) against a pressure of 1.0 atm at 125^∘ C, what is ΔU for this reaction?

Step 1:u000AFirst, we need to calculate the work done by the system. The work done by the system in

Consider the reaction 2 H2O(g) ⟶ 2 H2(g)+O2(g) Δ...

Consider the reaction $$\begin{array}{r}2 \mathrm{H}_{2} \mathrm{O}(g) \longrightarrow 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \\\Delta H=483.6 \mathrm{kJ} / \mathrm{mol}\end{array}$$ If 2.0 moles of $\mathrm{H}_{2} \mathrm{O}(g)$ are converted to $\mathrm{H}_{2}(g)$ and $\mathrm{O}_{2}(g)$ against a pressure of $1.0 \mathrm{atm}$ at $125^{\circ} \mathrm{C},$ what is $\Delta U$ for this reaction?

Consider the reaction $$\begin{array}{r}2 \mathrm{H}_{2} \mathrm{O}(g) \longrightarrow 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g) \\\Delta H=483.6 \mathrm{kJ} / \mathrm{mol}\end{array}$$
If 2.0 moles of $\mathrm{H}_{2} \mathrm{O}(g)$ are converted to $\mathrm{H}_{2}(g)$ and $\mathrm{O}_{2}(g)$ against a pressure of $1.0 \mathrm{atm}$ at $125^{\circ} \mathrm{C},$ what is $\Delta U$ for this reaction?

Key Concepts

Change in Moles of Gas (?n)

The change in the number of moles of gas (?n) during a reaction is a crucial factor in calculating pressure-volume work. It represents the difference in the total moles of gaseous products and reactants. In reactions where gases are involved, this change directly impacts the relationship between enthalpy and internal energy, influencing the overall energy balance of the system.

Ideal Gas Law

The ideal gas law, expressed as PV = nRT, connects pressure (P), volume (V), temperature (T), and number of moles (n) using the gas constant (R). This equation is fundamental for calculating properties of gases during chemical reactions, such as determining the work performed during expansion or compression in thermodynamic processes.

Enthalpy Change (?H)

Enthalpy is a measure of the total heat content of a system at constant pressure. In reactions, the enthalpy change (?H) represents the heat absorbed or released. It includes both the internal energy change and the work done by the system, particularly when gases expand or contract, making it a central concept in thermochemistry.

Internal Energy Change (?U)

Internal energy is the sum of all forms of energy contained within a system, including kinetic and potential energies of molecules. The change in internal energy (?U) is the net result of energy exchange under constant volume conditions. In thermodynamic reactions, the relationship between ?U and other quantities like ?H provides insight into the energy changes occurring during chemical transformations.

Pressure-Volume Work

Pressure-volume work is the work done by a system when it expands or contracts against an external pressure. In reactions involving gases at constant pressure, this work is significant and is related to the change in the number of moles of gas. This concept is critical in understanding how the energy supplied as heat divides between changing internal energy and doing work against the surroundings.

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