For combustion of one mole of magnesium in an open container at 300 K and 1 bar pressure, $\Delta_{\mathrm{C}} \mathrm{H}^{\ominus} =-601.70 \mathrm{~kJ} \mathrm{~mol}^{-1}$, the magnitude of change in internal energy for the reaction is ______ kJ. (Nearest integer) (Given : $\mathrm{R}=8.3 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$)

JEE Main · 2022 · 28 Jun 2022 · Shift 2 · Chemical Thermodynamics

For combustion of one mole of magnesium in an open container at 300 K and 1 bar pressure,

Δ_{C} H^{⊖} = - 601.70 kJ mol^{- 1}

, the magnitude of change in internal energy for the reaction is ______ kJ. (Nearest integer)
(Given :

R = 8.3 J K^{- 1} mol^{- 1}

)

Answer: 600

The combustion reaction is:

Mg (s) + \frac{1}{2} O_{2} (g) \to MgO (s)

Using the relation

Δ H = Δ U + Δ n_{g} R T

where

Δ n_{g} = 0 - 0.5 = - 0.5

- 601.70 = Δ U + (- 0.5) \times 8.3 \times 1 0^{- 3} \times 300

- 601.70 = Δ U - 1.245

Δ U = - 600.455

kJ

Magnitude = 600 kJ

JEE Main · 2022 · 28 Jun 2022 · Shift 2 · Integer answer