We can calculate the final temperature from this formula :
when Tf = (V1* T1) +(V2* T2) / (V1+ V2)
when V1 is the first volume of water = 5 L
and V2 is the second volume of water = 60 L
and T1 is the first temperature of water in Kelvin = 80 °C +273 = 353 K
and T2 is the second temperature of water in Kelvin = 30°C + 273= 303 K
and Tf is the final temperature of water in Kelvin
so, by substitution:
Tf = (5 L * 353 K ) + ( 60 L * 303 K) / ( 5 L + 60 L)
= 1765 + 18180 / 65 L
= 306 K
= 306 -273 = 33° C
When a substance absorbs thermal energy, it partitions some as potential and some as kinetic energy. Specific heat is an expression related to the quantity of heat a substance stores as potential energy; the remainder is absorbed as kinetic which causes the temperature to increase - recall that temperature is a measure of average kinetic energy.
When specific heat is low, most of the energy is partitioned as kinetic energy and the substance will experience the greatest temperature change.
So rather than calculating the change in temperature, we can simply inspect the specific heats. The one with the lowest will experience the greatest temperature change. We could also compare the specific heats: Al = .897/.385 ==> 2.3, Fe = .452/.385 = 1.2, Cu = .385/.385 = 1. We can expect Copper's temperature change to be 2.3 times larger than Aluminum's and 1.2 times larger than Iron's.
The answer is (3) moles of solute per liter of solution. That is what the definition of molarity of a solution means. The equation is concentration = mol number of solute/ volume of solution.
