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Scienc

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  1. What is the physical meaning of enthalpy?
  2. The volume that 6 moles occupy 134.4l and 12 moles occupy 268.8 moles, since 1 mol = 22.4l, for this the gas needs to expand
  3. What is the difference between the work done by a gas and the workflow that the same gas performs to exist? why does the variation in the internal energy of the equation dH = dQ + nRT not consider the work done by the gas to exist (working flow) but consumes only the heat transfer? In the question below, the author considers dU = Q. He performs the calculation of the work done by the gas, separated from the internal energy (with an equation dH = dU + nRT ). If you know that in systems with constant volume dU = Q, but the gas volume varies (From 6 moles to 12 moles of gas), this does not imply an internal energy variation equal to dU = w + q (As stated in the 1st law of thermodynamics) and why consider dU = w + q and not dU = Q **? In practice or in what he did, the logic he did not use was. Question: “A constant volume calorimeter showed that the fuel loss in burning 1 mole of glucose is equal to -2559kJ in 298K, that is dU = -2555KJ”
  4. Scienc

    Enthalpy

    Thank you. Thank you.
  5. A variation of enthalpy at constant pressure is numerically equal to the variation of heat in a chemical reaction, but what is enthalpy in itself? what is its difference for internal energy, is it calculated as H = U + PV, or does that mean physically?
  6. Guys, why in physics does the work done by the system have the POSITIVE sign, but in chemistry does the work done by the system have the NEGATIVE sign?
  7. Why does the equation τ = -n.R.T.ln⁡ (v_2 / v_1) only work for reversible processes?
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