Answer to Question #320003 in Physical Chemistry for ASDFGJKL

Question

Calculate the differences in energy between ΔU and ΔH for the following reactions at constant pressure at 25^oC.(use ΔH = ΔU + PΔV)

a) CH3CH2CH3(g) + 5O2(g) ⇔ 3CO2(g) + 4H2O (l)

b) C6H12O6 (s)+6O2(g) ⇔ 6 CO2(g) + 6 H2O(l)

c) Mg (s) + 2H + (aq) ⇔ Mg2(aq) + H2(g)

Answer 1

ΔH = ΔU + PΔV

ΔU - ΔH = -PΔV

For the reaction (a): 5O₂ = 3CO₂ (ΔV < 0, PΔV = max)

For the reaction (b): 6O₂ = 6CO₂ (ΔV = 0, PΔV = 0)

For the reaction (c): 1 mol H₂ is produced (ΔV > 0, PΔV = min)