When 1 mole of Na(s) is dissolved in large volume of water at 298 K and 1 bar, 184 kJ/mol heat is released. When 1 mole of (s) is dissolved in large volume of water at 298 K and 1 bar, 238 kJ/mol. If

Question

When 1 mole of Na(s) is dissolved in large volume of water at 298 K and 1 bar, 184 kJ/mol heat is released. When 1 mole of $Na_2O$(s) is dissolved in large volume of water at 298 K and 1 bar, 238 kJ/mol. If the enthalpy of formation of water is -286 kJ/mol, then the enthalpy of formation of sodium oxide is

Prashant Kotian · Accepted Answer

Correct answer: C. Combining: (1) 2Na(s) + 2(l) -> 2(aq) + (g); dH = 2*(-184) = -368 kJ. (2) 2(aq) -> (s) + (l); dH = +238 kJ. (3) (g) + 1/2 (g) -> (l); dH = -286 kJ. Sum: 2Na(s) + 1/2 (g) -> (s); delta_f H = -368 + 238 - 286 = -416 kJ/mol.

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