Chemistry Calculate Qv from Qp: deltaH and deltaU

Thread starter aruhland
Start date Jan 27, 2020

AI Thread Summary

The discussion focuses on calculating Qv from Qp using the relationships between deltaH and deltaU. It confirms that Qp equals deltaH and Qv equals deltaU, with the equation Qv = deltaH - deltanRT being central to the calculations. The user attempts to compute Qv as -2001.42 kJ/mol but finds it incorrect for their assignment. Participants suggest reviewing the algebra and clarifying the change in the number of moles of gas (Δn) to ensure accurate calculations. The conversation emphasizes the importance of precise calculations in thermodynamic equations.

Jan 27, 2020

aruhland

Homework Statement: For the reaction below, constant pressure heat of reaction is Qp=-2051 kj/mol at 25 C. What is the constant volume heat of reaction, Qv, at 25 C?

10CO(g) + 21H2(g) --> C10H22(l) + 10 H2O(l)

Relevant Equations: enthalpy change=internal energy change + change in mol=*R*T
internal energy change=Qv-Pext*volume change

Qp=deltaH
Qv=deltaU
deltaH=deltaU + deltanRT
Qv=deltaH - deltanRT
=-2051 kj/mol - (11mol-31mol)(8.3145x10-3J/Kmol)(298.15K)
=-2001.42 kJ/mol

I thought I did this correctly but it comes up as wrong for my online assignment. Any suggestions?

deltaH=enthalpy change
deltaU=internal energy change

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Jan 27, 2020

Chestermiller

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Check your algebra

Jan 28, 2020

mjc123

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What is Δn? Change in number of moles of gas...

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