Defining q and relation to p, v, and enthalpy

[Bradley Bohall 3L]

What is q and how does that relate to qp and qv? Why can we say that qp is equal to enthalpy change?

[tristenaguinaldo]

qv is heat at a constant volume while qp is heat at a constant pressure. qp is usually measured with a calorimeter while qv can be measured with a bomb calorimeter.qp also equals delta H or enthalpy where pressure is constant. At a constant volume, deltaU = qv, since no work of expansion is being done on the system. At a constant pressure, deltaU = deltaH- pdeltaV. Qp is always equal to enthalpy.

[Louie_Reichmuth_2K]

q represents heat. qv represents heat at a constant volume; qp represents heat at a constant pressure. DeltaH = qp - PdeltaV. But here the pressure is constant so DeltaH simply equals qp.

[yvette nouneh]

The variable q is a representation of heat. When given the subscript v (volume), this variable becomes qv, which signifies the heat of a substance at constant volume. When given the subscript p (pressure), this variable becomes qp, which signifies the heat of a substance at constant pressure. We know that DeltaH= qp-PdeltaV. When pressure is constant, we see that qp will equal DeltaH.

[Ellie Garcia 2L]

Hi Bradley!

In thermodynamics, "q" is a symbol that represents the heat transfer in a system. It is typically used in equations that describe the changes in the internal energy (U) of a system. The sign convention for q is such that a positive value of q indicates that heat is added to the system, while a negative value of q indicates that heat is removed from the system.

"qp" is a symbol that is used to represent the heat transfer that occurs in a constant-pressure process. The "p" in "qp" stands for "pressure." The value of qp is equal to the change in enthalpy (ΔH) of a system, which is the sum of its internal energy (U) and the product of its pressure (P) and volume (V). This relationship can be expressed as:

ΔH = qp = U + PV

Similarly, "qv" is a symbol that is used to represent the heat transfer that occurs in a constant-volume process. The "v" in "qv" stands for "volume." The value of qv is equal to the change in internal energy (ΔU) of a system. This relationship can be expressed as:

ΔU = qv

In summary, q, qp, and qv are related to each other in that they are different ways of representing the heat transfer that occurs in a thermodynamic system. The value of qp is equal to the change in enthalpy of a system, while the value of qv is equal to the change in its internal energy.

Hope this helps! ^^

[205750231]

Q is defined as the net heat transfer of a system. Qp is the net heat transfer at constant pressure, and Qv is the net heat transfer at constant volume. For Qp;

delta H = Qp = U + pV

Since Qp is the net heat transfer at constant pressure, Qp is equal to the change in enthalpy.

[Shiraz Becker 2A]

The constant q represents heat transfer. When q has a subscript v, it indicates the heat transfer at a constant volume. Likewise, q with a subscript of p indicates the heat transfer at a constant pressure. We say that enthalpy change equals qp because if there is 0 change in pressure then pDeltaV will equal zero in the equation for enthalpy change, so delta H will equal qp + 0.