Calculate Qv from Qp: deltaH and deltaU

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In summary, Qv and Qp are both measures of heat, but Qv represents heat transfer at constant volume while Qp represents heat transfer at constant pressure. To calculate Qv from Qp, the equation Qv = Qp + PΔV is used, taking into account the work done by the system. DeltaH (ΔH) is the change in enthalpy of a system, while DeltaU (ΔU) is the change in internal energy. Qv and Qp can have the same value if the process occurs at constant volume and pressure, but this is not always the case.
  • #1
aruhland
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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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What is Δn? Change in number of moles of gas...
 
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FAQ: Calculate Qv from Qp: deltaH and deltaU

1. How do you calculate Qv from Qp?

To calculate Qv from Qp, you can use the equation Qv = Qp + deltaH - deltaU, where deltaH is the change in enthalpy and deltaU is the change in internal energy.

2. What is the difference between Qv and Qp?

Qv and Qp both represent heat, but Qv is the heat at constant volume and Qp is the heat at constant pressure. Qv takes into account the work done by the system, while Qp does not.

3. How do you determine deltaH and deltaU?

DeltaH and deltaU can be determined by calculating the difference between the final and initial values of enthalpy and internal energy, respectively. They can also be determined using experimental data or thermodynamic tables.

4. Can Qv be negative?

Yes, Qv can be negative. A negative Qv indicates that the system is losing heat to the surroundings.

5. What units are used for Qv and Qp?

Qv and Qp are both measured in joules (J) or kilojoules (kJ), since they represent heat, which is a form of energy.

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