Question

The enthalpy change, ΔH, for a reaction at constant pressure is defined as:

ΔH = ΔE + PΔV.

For which of the following reactions will ΔH be approximately equal to ΔE?

Select all that apply.

Group of answer choices

2 NO₂(g) -> N₂(g) + 2 O₂(g)

Ca(OH)₂(aq) + H₂SO₄(aq) -> 2 H₂O(l) + CaSO₄(s)

C(s) + O₂(g) -> CO₂(g)

None of the above

Answer 1

ΔH = ΔE + PΔV

There will be no change in volume if number of mol of gas on both sides of chemical equation is same

option 1:

reactant has 2 molecules of gas

product has 3 molecules of gas

option 2:

reactant has 0 molecules of gas

product has 0 molecules of gas

Molecule of gas is same on both sides.

So, ΔH be approximately equal to ΔE

option 3:

reactant has 1 molecules of gas

product has 1 molecules of gas

Molecule of gas is same on both sides.

So, ΔH be approximately equal to ΔE

Answer: option 2 and 3