Consider the reaction N2 +3H2 - 2NH3 carried out at constant temperature and pressure. If ΔH and ΔU are the enthalpy and internal energy changes for the reaction, which of the following expressions is true ?

Question

Consider the reaction N2 +3H2 -> 2NH3 carried out at constant temperature and pressure. If ΔH and ΔU are the enthalpy and internal energy changes for the reaction, which of the following expressions is true ? (A)  ΔH > ΔU  (B)  ΔH < ΔU  (C)  ΔH = ΔU  (D)  ΔH = 0

Tardigrade Admin · Accepted Answer

Δ H=Δ U+Δ ng RT ΔH = enthalpy change (at constant pressure) ΔU = internal energy change (at constant volume) (given reaction is exothermic) Δng = mole of (gaseous products - gaseous reactants) =-ve Thus, ΔH < ΔU

Q. Consider the reaction
$N X_{2} + 3 H X_{2} 2 NH X_{3}$
carried out at constant temperature and pressure. If $Δ H$ and $Δ U$ are the enthalpy and internal energy changes for the reaction, which of the following expressions is true ?

$Δ H > Δ U$

$Δ H < Δ U$

$Δ H = Δ U$

$Δ H = 0$

$Δ H = Δ U + Δ n_{g} RT$
$Δ H =$ enthalpy change (at constant pressure)
$Δ U =$ internal energy change (at constant volume) (given reaction is exothermic)
$Δ n_{g} =$ mole of (gaseous products $-$ gaseous reactants)
$= - v e$
Thus, $Δ H < Δ U$

Q. Consider the reaction NX2​+3HX2​​2NHX3​ carried out at constant temperature and pressure. If ΔH and ΔU are the enthalpy and internal energy changes for the reaction, which of the following expressions is true ?

ΔH>ΔU

ΔH<ΔU

ΔH=ΔU

ΔH=0