How to calculate the value of internal energy change when enthalpy change for the reaction N2(g) 3h2(g) -- 2NH3(g) is 91.8 KJ at 298 k? (R= 8.314 J /k mol)?

Question

How to calculate the value of internal energy change when enthalpy change for the reaction N2(g)   3h2(g) -- 2NH3(g) is 91.8 KJ at 298 k? (R= 8.314 J /k mol)?

Answer

Answer

Calculating Internal Energy Change from Enthalpy Change

To calculate the internal energy change of a reaction, we need to use the relationship between enthalpy change, internal energy change, and the work done by the system.

The Formula for Calculating Internal Energy Change

The formula for calculating the internal energy change is:

ΔU = ΔH - PΔV

Where:

ΔU is the change in internal energy
ΔH is the change in enthalpy
P is the pressure
ΔV is the change in volume

Calculating Internal Energy Change for the Given Reaction

Given the reaction:

N2(g) + 3H2(g) → 2NH3(g)

The enthalpy change for the reaction is 91.8 kJ at 298 K. We can use the formula above to calculate the internal energy change.

Step 1: Calculate the Work Done by the System

Since the reaction is at constant pressure, we can assume that the work done by the system is equal to the product of the pressure and the change in volume:

PΔV = 0 (since there is no change in volume)

Step 2: Calculate the Internal Energy Change

Now we can use the formula to calculate the internal energy change:

ΔU = ΔH - PΔV
ΔU = 91.8 kJ - 0
ΔU = 91.8 kJ

Therefore, the internal energy change for the given reaction is 91.8 kJ at 298 K.

Final Thoughts

The calculation of internal energy change from enthalpy change requires an understanding of the relationship between the two and the work done by the system. By using the formula provided, we can calculate the internal energy change for any given reaction.

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