Solution :
a). Applying the energy balance,



![$0=[mc(T_f-T_i)_{iron}] + [mc(T_f-T_i)_{water}]$](https://tex.z-dn.net/?f=%240%3D%5Bmc%28T_f-T_i%29_%7Biron%7D%5D%20%2B%20%5Bmc%28T_f-T_i%29_%7Bwater%7D%5D%24)


b). The entropy change of iron.


= -9.09 kJ-K
Entropy change of water :


= 10.76 kJ-K
So, the total entropy change during the process is :

= -9.09 + 10.76
= 1.67 kJ-K
c). Exergy of the combined system at initial state,






Therefore, energy of the combined system at the initial state is

= 63.94 -13.22
= 50.72 kJ
Similarly, Exergy of the combined system at initial state,





Thus, energy or the combined system at the final state is :

= 216.39 - 9677.95
= -9461.56 kJ
d). The wasted work



= 50.72 + 9461.56
= 9512.22 kJ
Data:
Molar Mass of Nickel = 58,7 g/mol
Solving:
58,7 g → 1 mol
y -------→ 2.63 mol
Solving: (They are proportional measures, the rule of three is made (directly proportional)

multiply cross

I think its the mass that changes but im not sure
<u>Answer:</u> The given sample of water is not safe for drinking.
<u>Explanation:</u>
We are given:
Concentration of fluorine in water recommended = 4.00 ppm
ppm is the amount of solute (in milligrams) present in kilogram of a solvent. It is also known as parts-per million.
To calculate the ppm of fluorine in water, we use the equation:

Both the masses are in grams.
We are given:
Mass of fluorine =
(Conversion factor: 1 g = 1000 mg)
Mass of water = 5.00 g
Putting values in above equation, we get:

As, the calculated concentration is greater than the recommended concentration. So, the given sample of water is not safe for drinking.
Hence, the given sample of water is not safe for drinking.