Chemistry - Thermochemistry Question with Solution | TestHub
Two bars of equal mass, one of aluminium (atomic mass 27) and one of copper (atomic mass 63.5), are heated to 80°C and then immersed in identical, insulated containers each containing 300 g of water at 25°C. Which bar causes the greater temperature rise in the water?
Options:
Answer:
Solution:
By the Dulong-Petit law, the molar heat capacity for both substances is approximately 25 J/mol·K. Therefore, the specific heat is approximately 25/atomic mass.
For aluminum (Al), the specific heat is approximately 0.93 J/g·K. For copper (Cu), the specific heat is approximately 0.39 J/g·K.
When equal masses of Al and Cu cool down, the heat released is given by the formula Q = msΔT, where m is mass, s is specific heat, and ΔT is the change in temperature. Since Al has a larger specific heat than Cu, the heat released by the Al bar upon cooling will be greater. Consequently, the water in contact with the Al bar will warm more. This corresponds to option (c).
