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
pls someone a) ?????????
-2.295 for a)
Thank you
Please mind your own answers--and business.
He has got a point, though he did it a bit too aggressively. What he wants to know is, what are the formulas for working out these two questions? After all, a similar question could pop up in the final exam! To tell you the truth, i kinda miss how it was at the beginning of the course, with people taking to the forums and asking for help with the formulas, and pointing out any mistakes in other people's posted formulas. people wrote the most beautiful things then. *Sigh* These days, it's just "The Answer is X" on sites like these.
To calculate the enthalpy of mixing for a solution of 10% platinum and 90% gold, we need to use the given value of delta w (-4250 J/mol).
(a) The enthalpy of mixing (delta H_mix) can be calculated using the formula:
delta H_mix = x_p * delta H_p + x_g * delta H_g
Where x_p and x_g are the mole fractions of platinum and gold, respectively, and delta H_p and delta H_g are the enthalpies of pure platinum and gold.
Since the solution is 10% platinum and 90% gold, the mole fractions can be calculated as follows:
x_p = 10/100 = 0.1
x_g = 90/100 = 0.9
Now, we substitute the values into the formula:
delta H_mix = (0.1 * delta H_p) + (0.9 * delta H_g)
Given that delta w = -4250 J/mol, we can convert it to kJ/mol:
delta w = -4250 J/mol = -4.25 kJ/mol
Now, let's assume that the enthalpy of pure gold (delta H_g) is zero. So, the equation becomes:
delta H_mix = (0.1 * delta H_p) + (0.9 * 0)
Therefore, delta H_mix = 0.1 * delta H_p = 0.1 * (-4.25 kJ/mol) = -0.425 kJ/mol.
So, the enthalpy of mixing for a solution of 10% platinum and 90% gold is -0.425 kJ/mol.
(b) Based on the given information, we can conclude that the dissolution of 10% platinum into gold is an exothermic process. This is because the change in enthalpy (delta H_mix) is negative (-0.425 kJ/mol). The negative value indicates that the process releases heat, which is a characteristic of an exothermic process.
Therefore, the correct choice is: i) Exothermic as the change in enthalpy is negative.