Consider the gold-platinum system which has a value of delta w of -4250 J/mole;
(a) Calculate the enthalpy of mixing for a solution of 10% platinum and 90% gold. Express your answer in units of kJ/mole.
(b) Is the dissolution of 10% platinum into gold an endothermic or an exothermic process?
i)Exothermic as the change in enthalpy is negative.
ii)Endothermic as the change in enthalpy is positive.
iii)Impossible to tell without considering the entropy of the system.
b) i
Any idea on (a)?
-2.295
The formula and explanation are given in the lecture video S23V2, in this case what you need to be cautious is the Z, Pt and Au are FCC structure, hence you need to draw the unit cell and its surrounding unit cell to get the idea of the coordination number.
To calculate the enthalpy of mixing for a solution of 10% platinum and 90% gold in the gold-platinum system, we need to use the given value of delta w (-4250 J/mole) and convert it to kJ/mole.
(a) Calculation:
1. Start with the given value of delta w: -4250 J/mole.
2. Divide it by 1000 to convert J to kJ: -4250 J/mole รท 1000 = -4.25 kJ/mole.
So, the enthalpy of mixing for a solution of 10% platinum and 90% gold is -4.25 kJ/mole.
(b) To determine whether the dissolution of 10% platinum into gold is an endothermic or an exothermic process, we need to analyze the sign of the change in enthalpy (delta H) for the process.
From the given information, we know that the value of delta w is -4250 J/mole, which is the change in enthalpy for the system. A negative value for delta H indicates an exothermic process, while a positive value indicates an endothermic process.
Therefore, option i) is correct: The dissolution of 10% platinum into gold is an exothermic process as the change in enthalpy is negative. The negative value (-4.25 kJ/mole) indicates that energy is released during the mixing process.