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In which one of the following processes is ΔH = ΔE?

a. 2HI(g) → H2(g) + I2(g) at atmospheric pressure.

b. Two moles of ammonia gas are cooled from 325°C to 300°C at 1.2 atm.

c. H2O(l) → H2O(g) at 100°C at atmospheric pressure.

d. CaCO3(s) → CaO(s) + CO2(g) at 800°C at atmospheric pressure.

e. CO2(s) → CO2(g) at atmospheric pressure.

  • chemistry -

    Delta E = delta H -p*delta V
    where work is p*delta v.
    So if delta v is zero, then there is no work and delta E = delta H = qp
    Note that when a reaction is at constant P, then a change in moles will result in a change in volume.
    For a)
    H2 + I2 ==>2HI
    The work is zero because p*delta V is zero (because there are two moles of gas on the left and two moles of gas on the right). No change in moles, no change in volume and delta v is zero.

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