# Mod4 Chem (1 Viewer)

#### kkk579

##### hello
I have a few inquiries:

1. Whats the difference between enthalpy and q (the q in q=mcdelta(t))

2. Why is a calorimeter with a higher specific heat capacity better?

#### liamkk112

##### Well-Known Member
i only know 1): Q = mc delta T refers to heat energy released or absorbed into a system. enthalpy, on the other hand, is defined as delta H = delta U + delta PV. in simple words, U is the energy currently in the system, and delta P V is the product of the change in pressure and volume, which can kind of be thought of as the work that is required to expand the system from V =0 to the current V against the pressure on the system (someone probably has a better explanation for this, i might be wrong). now if the change in pressure is 0, then we just get delta H= delta U. and by the first law of thermodynamics, delta u = Q - W, but we established that if delta PV = 0, then the "work" term becomes 0, so we assume that W = delta PV =0. so now delta H = Q = mc delta T. in other words, when something is at a constant pressure and volume, then the change of enthalpy is exactly equal to the change in heat energy into the system.

#### kkk579

##### hello
i only know 1): Q = mc delta T refers to heat energy released or absorbed into a system. enthalpy, on the other hand, is defined as delta H = delta U + delta PV. in simple words, U is the energy currently in the system, and delta P V is the product of the change in pressure and volume, which can kind of be thought of as the work that is required to expand the system from V =0 to the current V against the pressure on the system (someone probably has a better explanation for this, i might be wrong). now if the change in pressure is 0, then we just get delta H= delta U. and by the first law of thermodynamics, delta u = Q - W, but we established that if delta PV = 0, then the "work" term becomes 0, so we assume that W = delta PV =0. so now delta H = Q = mc delta T. in other words, when something is at a constant pressure and volume, then the change of enthalpy is exactly equal to the change in heat energy into the system.
Ive only done the start of mod4 and haven5 finished it so i havent rlly encountered any of the stuff youre saying like delta U and pv

#### liamkk112

##### Well-Known Member
Ive only done the start of mod4 and haven5 finished it so i havent rlly encountered any of the stuff youre saying like delta U and pv
just understand then that Q is specifically about heat energy in a system whereas enthalpy is also inclusive of other energies in a system

#### kkk579

##### hello
just understand then that Q is specifically about heat energy in a system whereas enthalpy is also inclusive of other energies in a system
Ohh okay, arent they both kinda the same thing then? like both measure the amount of energy in a system, just that q is restricted specifically to heat

#### kkk579

##### hello
Ohh okay, arent they both kinda the same thing then? like both measure the amount of energy in a system, just that q is restricted specifically to heat
Because in my peak booklet theres the formula
delta H (solute) = q(solute)/ no. of mols (solute)

#### liamkk112

##### Well-Known Member
Because in my peak booklet theres the formula
delta H (solute) = q(solute)/ no. of mols (solute)
that’s probably referring to the enthalpy per mole

#### kkk579

##### hello
that’s probably referring to the enthalpy per mole
Yeah exactly but doesnt that mean that q and H are essentially the same thing if theyre using q to determine enthalpy per mole

#### liamkk112

##### Well-Known Member
Yeah exactly but doesnt that mean that q and H are essentially the same thing if theyre using q to determine enthalpy per mole
only in some situations, otherwise that PV term is therw