Chemistry - Thermochemistry Question with Solution | TestHub
Calculate the heat effect produced when a solution of 1 mole of ethanol in 5 moles of water is mixed with a solution of 2 moles of ethanol in 20 moles of water. Given that,
C2H5OH + 5H2O → C2H5OH (5H2O); ΔH = -1120 cal
C2H5OH + 10H2O → C2H5OH (10H2O); ΔH = -1760 cal
C2H5OH + 25/3 H2O → C2H5OH (25/3 H2O); ΔH = -1650 cal
Options:
Answer:
Solution:
Initial state: 1 mol ethanol in 5 H₂O and 2 mol ethanol in 20 H₂O. (This is equivalent to 1 mol in 10 H₂O, taken twice).
The initial enthalpy, Hinitial, is calculated as:
Hinitial = (-1120) + 2(-1760) = -4640 cal
Final state: 3 mol ethanol in 25 mol water. This can be viewed as 3 mol of "ethanol in 25/3 H₂O".
The final enthalpy, Hfinal, is calculated as:
Hfinal = 3(-1650) = -4950 cal
The change in enthalpy, Δ H, is:
Δ H = Hfinal - Hinitial = -4950 - (-4640) = -310 cal
Since Δ H is negative, 310 cal of heat is released. This corresponds to option (b).
