Respuesta :
To illustrate clearly, I will rewrite the reaction in a more understandable manner.
2PbS (s) + 3 O₂(g) ⇒ 2 PbO(s) + 2 SO₂ (g) Δh = –827.4 kJ
Galena is PbS and Lead Oxide is PbO. This reaction has a negative sign for the change in enthalpy of reaction. The sign convention only means that the reaction releases energy to the surroundings. In other words, the reaction is exothermic. Focusing on only its magnitude, this means that 827.4 kJ of energy is needed for this reaction of 2 moles of Galena and 3 mole of O₂ to occur.
Now, if you had an energy of 975 kJ, then the reaction would proceed into completion and would even exceed in the number of moles of products produced. We use stoichiometric calculations as follows:
975 kJ * (2 mol PbS/827.4 kJ) = 2.357 moles of PbS
Knowing that the molar mass of Galena is 239.3 g/mol, then the mass of galena needed to produce PbO is
2.357 mol PbS *239.3 g/mol = 564 g galena
2PbS (s) + 3 O₂(g) ⇒ 2 PbO(s) + 2 SO₂ (g) Δh = –827.4 kJ
Galena is PbS and Lead Oxide is PbO. This reaction has a negative sign for the change in enthalpy of reaction. The sign convention only means that the reaction releases energy to the surroundings. In other words, the reaction is exothermic. Focusing on only its magnitude, this means that 827.4 kJ of energy is needed for this reaction of 2 moles of Galena and 3 mole of O₂ to occur.
Now, if you had an energy of 975 kJ, then the reaction would proceed into completion and would even exceed in the number of moles of products produced. We use stoichiometric calculations as follows:
975 kJ * (2 mol PbS/827.4 kJ) = 2.357 moles of PbS
Knowing that the molar mass of Galena is 239.3 g/mol, then the mass of galena needed to produce PbO is
2.357 mol PbS *239.3 g/mol = 564 g galena