Given the thermochemical equation:
2ZnS(s) + 3O2(g) „³ 2ZnO(s) + 2SO2(g) £GH = --879 kJ
Calculate the heat evolved (in kJ) when 560 grams of ZnS is converted to ZnO.
Please explain throughly with answers.
879 kJ are released when 2 moles (97.46 x 2 = 194.92 g) are used. So 560 g converted will be proportional to that.
879 kJ x (560g/194.92 g) = ?? kJ.
-136kj
To solve this problem, we will use the concept of stoichiometry and the given thermochemical equation.
First, let's determine the molar mass of ZnS and ZnO.
The molar mass of ZnS can be calculated as follows:
Molar mass of Zn: 65.38 g/mol
Molar mass of S: 32.07 g/mol
Molar mass of ZnS = (65.38 g/mol) + (32.07 g/mol) = 97.45 g/mol
The molar mass of ZnO can be calculated as follows:
Molar mass of Zn: 65.38 g/mol
Molar mass of O: 16.00 g/mol
Molar mass of ZnO = (65.38 g/mol) + (16.00 g/mol) = 81.38 g/mol
Next, we will calculate the number of moles of ZnS in 560 grams using the molar mass of ZnS:
Number of moles of ZnS = mass / molar mass = 560 g / 97.45 g/mol ≈ 5.74 mol
Now, we will use the stoichiometry of the thermochemical equation to determine the moles of ZnO produced.
According to the equation, 2 moles of ZnS produce 2 moles of ZnO.
So, the moles of ZnO produced = (5.74 mol ZnS) × (2 mol ZnO / 2 mol ZnS) = 5.74 mol
Finally, we can use the given enthalpy change to calculate the heat evolved:
Heat evolved = moles of ZnO produced × enthalpy change
= 5.74 mol × (--879 kJ/mol) ≈ -5045.46 kJ
Therefore, the heat evolved (in kJ) when 560 grams of ZnS is converted to ZnO is approximately -5045.46 kJ. The negative sign indicates that the reaction is exothermic, meaning heat is released.